Serious upgrade options in Mini Server or high-end Mini?

I intend to do two upgrades in my (about-to-be-bought) Mini Server -- and I hope to do a third upgrade (see below). Depending on answers to questions below, I may stick with the high-end non-Server model and do heavier upgrades from there... please read on...

• First, I'll upgrade to 8 GB ram using OWC or Crucial or whomever.

• Second, I'll upgrade the hard drives, and then, perhaps, the graphics.

So, question 1: how large (capacity) a hard drive will the power supply and heat-dissipation in the new Minis support? Any difference in power-supply capacity and heat dissipation between the high-end Mini and the Server model? I'd like to get at least one 1.5 TB drive, two if possible, in the Mini to duplicate my about-to-be-retired G5 desktop monster. Advice? Forseeable problems?

And third (finally!), I'd like to get that AMD Radeon HD 6630M graphics chip into my Server model to help me run even better video production with FinalCutPro X (and the FCP 7 that I intend to reinstall from my current desktop). I need the mini's portabiity, but (see Question 6) a laptop won't do the job.

Question 2: Can I reasonably expect to back-install the HD 6630M graphics chip to replace the Server model's 3000 graphics chip? (This one worries me; playing pull-and-punch with ANY logic board is no fun...)

Question 3: Alternatively, should I buy the highest-end non-Server model, which will give me the HD 6630M -- and then, try to replace its I7 dual-core with an I7 quad-core? I get the quad-core with the Server, but can't get the 6630M graphics, so can I create those options more easily by futzing with the high-end regular Mini?

Question 4: As first mentioned above, is there enough of a difference in the robustness of the power supply between the high-end regular Mini and the Server Mini that I would need to worry about replacing the stock 5400 rpm drives with BIGGG 7200 rpm drives, as I mentioned above? Any related, forseeable problems with that?

Question 5: Any major downside to killing off Lion and installing Snow Leopard? Not sure I'll do that, but I would like to retain Rosetta access for the very occasional instance where I need file compatibility with older high-end software.

Question 6: Any better ideas? No, I don't want to buy a MacBook Pro or a Pro -- I need portability but I don't need the laptop screen or its keyboard limitations. I'd like to do this with a Mini of some kind, and I will perhaps even save some money in the process (alhough there will be some serious elbow-grease and eyestrain expended).

FYI -- I already have two Minis of 2010 model, a Macbook Pro around 18 months old, the G5, and and older iMac.

Thoughts? Help? Ridicule? I'll take what I can get. Thanks!