If Tri-SLi support is un-needed, i personally wouldn't worry about it. Just get a new card that would be faster/asfast as your old one's in SLi.
Well they are basically the same as far as i can see. Go for the cheapy Gskills. I'm considering such a set to complement...
perhaps he doesn't wish to fart around with OC'ing.
Some applications other than games it's much better to have the quicker 100% stable chip doing it right every time.
Video encoding is one such application IMHO.
I went for a similar setup to you OP. Simply because when oc'd the E21x0's out run ANY standard dual core. upto the E6750. And gives the E6850 somthing to think about as well. Now since you have a Quad on the way. I suggest using the E2140 to power a new GF bulid. And see if you can score...
Ack. Even with out that Video card you'd fail. Go forth and get something cool like that Corsair 750VX. ( on special for 99 after MIR) If you're the type that upgrades a lot.
Or A Silverstone/Enermax 600-650 is another forward looking choice. Realistically 500 is all you need. But with Video...