Yeah I hate the asymmetry of the MBP and two monitors. Having the MBP front and center makes the main display your worst, but at least it's symmetrical. If you put it off to the side the whole thing is off kilter.
I have a mac pro as well, but I don't work on my own so much these days, so I've been perpetually putting off upgrading hardware. It is a 1,1, and I have to be careful on settings in certain applications and things to minimize lag. Anyway I have done a similar setup to you on my 2011 macbook pro. I have two screens, and I always semi-retire the older one with shifted colors and things when it gets old, then make the newer one the primary display. It doesn't matter as much if an old display is just holding notes and reference material, but I don't know of a way to hook up both a 1920x1200 and 1600x1200 (old one) display to a mbp, so the older one basically stays tied to my mac pro in spite of having both mini displayport to displayport and dvi-d (I think dvi-d) cables.
Aside from that the notebook runs small Xcode projects well, but I've never put anything through it that's large enough to really bog the thing down. I wouldn't even attempt the project you mentioned. The quad nMP would be less of a mess when it comes to storage if I ditched the older eSATA stuff, but it's not in my budget for now.
I've got 16GB in there which seems plenty enough.
It's only a hindrance for a subset of what I do, basically if I have to deal with heavy 3d scenes or photo comps, which I rarely do these days, ram can be a precious commodity due to seemingly geometric memory footprints.