A Dillon 550 or 650 would be your best bet.   For the .50 BMG, you'll probably want to buy a separate single stage press.  It's so big that you won't be able to load it on a progressive.

A good place to buy from is BrianEnos.com.   His website offers package deals that make ordering all the stuff easy.   

You shoot so many calibers that it will be hard to have just one or two reloading setups.
It might take as much time to change one press over from one caliber to another as for the actual reloading.
Unless you do marathon reloading sessions for one caliber, and then change the press and stuff over for another, it's a real pain.
If you decide to change the recipe, the huge pile of reloads are now kind of expensive dust collectors.
You might want to consider separate, inexpensive, but effective, presses, like a turret, for each of the handguns.
Then each can be quickly used as needed.
Then maybe something sturdy for the rifles, like the Dillon or Hornady LNL progressives for the high volume one and maybe a separate single stage for the low volume bolt action round.
But, unless you are looking forward to reloading, as an enjoyable hobby in its own right, you can see where this is going.
Lots of money for equipment and lots of time to reload for all these calibers.
Just a thought - or two.

That 50 BMG?  RCBS Rockchucker Supreme.  It's a single stage, but it also has 2 things you need for 50 BMG reloading:

1. The strength to re-size that big case.

2.  The ability to accept the special 50 BMG dies.

A progressive press basically does everything for you except place the slug in the case mouth automatically.  There are even companies out there that build adapters to do that.  But you're talking serious money here.

A case feeder?  Just what it says.  It automatically feeds cases to the progressive press, saving time and fingerprints on brass.  Usually a couple hundred bucks.

Where you're just starting out, I'd get the rockchucker supreme kit from somewhere local or midway along with at least 2 other reloading manuals and make sure reloading is something you want to get into heavily before laying out big bucks.

I'm not sure if I'll be reloading for high-volume stuff, just so long as I can get factory ammo cheaply; however, I do want the ability to do so.  My .308 Win.: I really need to roll my own for that one if I'm to squeeze out every ounce of accuracy I can.

I looked at brianenos.com and I'm thinking that I'll either get one of the starter kits there, or just buy a Lee anniversary loading kit off of Cabela's.  I won't be firing a whole lot of the .50BMG, so I think I can get away with a single-stage press since I won't need to use full-sized case dies on it (assuming of course I can find some rounds that are boxer-primed--currently, I'm stuck with using berdan-primed mil-surplus stuff).

I currently have 2k rounds of M118 168gr FMJBT rounds from Igman that are boxer-primed in military brass, when I get down to about 500 rounds of that, I'll clean up my brass and reload them in small batches and fiddle around with primers, charge weights, seating depths, different bullets, different powders, etc. in order to improve from ~1MOA down to a hopeful .5MOA.  Possible, yes; realistic: it has yet to be seen.  Only one way to find out though.

5.56x45mm is a totally different matter altogether--I've used about 2500 rounds of PMC Bronze 55gr FMJ rounds and I have maybe 50 cases that aren't bent to hell and back (both the Mini-14 AND RRA AR-15 tear up the brass, a crease in the brass that puts the neck at about a 10-degree angle to the case walls ).  I'm looking at buying a few thousand more rounds of Lake City M855 SS109 62gr FMJBT so I can have some brass to reload with.  :giggidy

As far as wanting to reload, I'm kindof iffy on it; however, with the way things are going now, I may have to reload to continue to shoot as much as I want to.  Also, there's the ability to squeeze out more accuracy with rounds I've rolled myself.  Money-saving is a distant second place as far as reloading goes--kindof like a lawful-good side-effect.

I know that, generally, I enjoy performing repetitive tasks that require attention to detail.  Those type things engage my mind and keep me from doing what I normally do when I have free time: think about things that aggravate me.

Nathan - Who will go to college not necessarily to get an education, but to give him something to do while he decompresses from a year out in the desert.  That is, of course, because I can't live a Charlie (Sheen) Harper lifestyle... 

I manage to save money.  A box of my loaded 9mm rounds cost me around 4-5 dollars.  Wolf at the local shops are going for over twice that.

G.wilikers-  Add almost any center fire rifle caliber to that list as well.

You do save money as far as cost per round, and in some cases, savings can be at or above the 80% mark vs. commercially produced ammunition, especially if the brass has been reloaded more than once, you cast your own bullets, and consider the time spent loading ammo as recreational time rather than work.

But you generally don't save raw dollars.  If you are used to spending say 100 bucks a week on ammo, you'll most likely still spend that same 100 bucks a week on components.  After loading them into assembled rounds, you'll have somewhere between 2 and 4 times as many rounds for your hundred dollars, but it's still 100 dollars spent.