Budget hardware upgrade options

Getting more and more into using After Effects and I'm noticing my system really gets bogged down on more detailed renders. I'm on a really tight budget and can't afford a new system or major upgrades, but I do have around $200 or so to put towards an upgrade until this summer when I'll have enough for a new build (I build my own custom rigs).

Current system:
Intel i7 920 (2.67GHz) running on a ASUS Sabertooth X58 motherboard
12 Gig of DDR3 PC3-16000 RAM
Windows 7 ultimate 64bit
HDD:
OS/Programs: 320G SATA 3.0 10,000rpm
DATA: 2T SATA 3.0 7200rpm (Includes 24Gig partition at the front of the HDD for system pagefile)
SCRATCH: 2T SATA RAID 0+1
Storage: 2x 3T USB 3.0

Until two months ago I was running a ATI/AMD Radeon HD5970 with 2Gig of GDDR5 but it died (it was a refurb) so I'm relegated to an old Radeon XT800 which isn't even PCIe x16 2.0 - it's a first gen PCIe x16 card. So I know that's one bottleneck in rendering. I can't imagine the RAM or CPU is much of a bottleneck - and I'm rendering to a scratch disc so I'm taking full advantage of the 6Gb/s throughput on that SATA channel.

Being on such a tight budget right now, my thinking is my dollars are best spent on a new GPU. My budget puts me in the lower end of the Quadro line which are certified for Adobe CS5. However ATI/AMD has a new budget card, the FirePro V4900 that seems to have much more bang for the buck than any Quadro in that price range. Just the fact that the V4900 has 1Gig of DDR5 seems to me to put it head and shoulders over any Quadro in that price range. But there's very little on-line about how well it works with CS5 and specifically After Effects. I've seen the FirePro V4900 in action with AutoCAD and was very impressed - far exceeds the capabilities of a higher end consumer card for that purpose. But again, there's nothing much that I can find on-line on how well the V4900 integrates with After Effects.

Now for a little bit more $$$, I can get a Radeon HD6870 with the same amount/type of RAM but a faster core clock speed, higher effective memory, twice the memory interface, and more processing units. The HD8670 is also crossfire capable - but I don't know if crossfire helps in terms of faster rendering (it helps immensely in gaming).

Or are there other/better upgrade options within my budget that will get me to the summer? I'm still leaning towards the GPU upgrade - and if I do, do I go with the budget professional card or the mid/upper level consumer card?

Well I do have 12Gig of RAM and my only real option would be to double that. I have all 6 slots filled right now (6 x 2Gig) - so I'd be looking at a 24Gig kit (6 x 4Gig). It seems to me that 12Gig should be fine for my needs at this point. And when summer rolls around I'd like to build a completely new rig based around the 6 core i7 Extreme Sandy Bridge LGA 2011 CPU. That wouldn't make all that RAM useless - but it would be seriously under-clocked based on the CPU, FSB, and the L cache.

That's why I'm really leaning towards a GPU upgrade - it would be reusable in my new system I'll build this summer without being a bottleneck based on what I want to build (unless the professional cards jump on the PCIe x16 3.0 bandwagon).

All kind of depends on what is slowing down the system. As you know, the more layers and effects you add on, the slower it will get - no matter what you put into it. That being said, if you are using a lot of effects that could benefit from openGL, then that may not be a bad upgrade, but your system does look pretty solid otherwise. Check out the AfterEffects card compatibility here: http://www.adobe.com/products/aftereffects/extend.html
That page has a list of the effects that it will help, so you can figure out if it's worthwhile to even do your upgrade before your big summer purchase.
TC