Many thanks :) I built this system on May 05, 2009, it's first CPU's were two Quad Core AMD OpteronDP 2380 C2 Shanghai's which gave me 8x 2.5Ghz but with Hyper Transport 1.1 and the system had two EVGA GTX 295 Red Editions in Quad SLI.
After the GTX 295 RE's it had 2-Way SLI with an EVGA & Zotac GTX 480 1.5GB's, 2x EVGA GTX 580 SC 1.5GB's and now with two EVGA GTX 680 SC Sig 2GB's. The Six-Core OpteronDP 2435 D0 Istanbuls were added in April 2012, as I grabebd a matched pair for 235 USD incl shipping & Insurance from USA to NL, and that is evry cheap for 12 cores, and that time I could not find any 1CPU that could compete with it for that money, it was a steal in otherwords.
The 2435's replaced the 2380's and my gains with rendering was about 61% boost and that for jsut 235 USD, go figure right ;)
So yeah it may be old but it has had a good history and it runs every game @ 1920 x 1200 in max settings without any issues what so ever in DX9, 10 and 11, like OpenGL 2.1 3.3 & 4.3.
So due to that I never saw any need for upgrading yet, the CPU's I use are plenty of real cores to my needs, 12 Cores 12 FPU's @ 2.6Ghz in total, so far no app ran too slow on this system, even being it's 4 years and 6 months old, it's lifespan for being a Dual CPU system and native SLI Support kinda did it.
It's PCI_E slots are PCI-E 1.1 x16 but with SLI they run with the full 32 Lanes, which is brilliant. So far I have not seen much difference between PCI-E 1.1, 2.0 & 3.0 x16 even with SLI setups, it seems that PCI-E 1.1 x16 seems to be plenty even when using PCI-E 3.0 x16 cards rofl.
With CUDA Apps the PCI-E bandwidth plays hardly a role it's mainly the GPPU performance that counts and two of these GK104-400-A2's is O-Plenty for I am seeking from such cards.
So yeah it's mobo may be old, but age doesn't mean much with 2CPU builds, these systems are famous for their very long lifespans over the conventional 1CPU setups.
As for a next system that would probably be a Dual E5 2660 or so with the ASUS Z9PE D8 WS, but so far that isn't needed as of yet