Nvidia said that the 400 series wouldnt cause a bottleneck on this motherboard (NvIdia 680i SL) with a 700W PS. I am not sure but I think that the primary PCI slot may not be a 12 volt rail (I have no idea what that means...I just retyped what a guy in our IT group told me) or its not getting all the power it needs from it.
But, how would one test that theory? My GTS 250 1 gig, DDR3 was doing fine...truthfully? Better than this 460.
Changeup
Somebody else could maybe speak more to the specifics of that motherboard/PS/card combination, it could very well be your video card is starved for power, but here's basically what I mean...
The easiest way to think of PC speed to me is like a chain. It's only as fast as its slowest link. CPU speed, amount of RAM, frontside bus speed, and video card are your main speed contributors. It's quite rare when it comes to gaming that your video card is not the thing working hardest in your system, but it does happen occasionally, and games that are using established game engines like AH tend to be one of those niches. AH is also apparently fairly reliant on CPU.
What I was basically saying was, assuming the rest of your system stayed the same, and the video card was the only thing that you upgraded, it somewhat indicates your video card might not be the slow link in the chain.
There's a lot of factors that contribute to speed, and the issue you're describing there sounds like it is probably going to be a decent sized pain in the backside to troubleshoot.
Before changing stuff, I'd sit down and consider whether 42fps in a big crowd is that bothersome to you or not. Does it affect your gameplay, or do you just notice the number drop? Either answer is fine, I'm just saying sometimes attempting to improve speed can make it worse. Consider if it's worth the risk.
The other thing to consider, if you have shadows on but don't really care if they are on or not, maybe try turning them off. They make a huge impact on frame rate, and if you don't mind having them off, that might be a quick solution too. It's up to you.
The absolute first thing I'd suggest is defrag your hard drive. It could be your system taking just a bit longer to access files while you're playing causing the frame rate dips. I've seen that happen in a lot of places, and it's the simplest fix to do. I'd defrag, then try playing for a while, see if it improves.
If there's no improvement, then you move on to other things.
The next thing I'd nail down is whether your video card is getting enough power. It's not an issue I've ever had, not quite sure how to troubleshoot it, I'd talk to your IT guru about it if possible.
If that's apparently ok, then I'd move on to some other things.
No offense intended if you're already aware of such things, but generally speaking the place to start is you'd want to make sure your drivers for everything are up to date unless HTC has a preferred set of drivers for that card that is downversion (haven't seen anything like that in a while now though).
Now by drivers for everything, I mean your motherboard chipset drivers, BIOS, sound, and video drivers. Quite often, motherboard drivers need tweaks as video card technology advances, or bugs are found, or whatever. People always talk about video and sound, but the BIOS and chipset drivers are also very important. Your motherboard manufacturer's website is where you'd go for those.
Understand also, these comments are just straight off the top of my head. Troubleshooting gaming performance is a pretty involved process, and the worst part is, sometimes it's a gamble whether the new versions of drivers will speed you up or slow you down, or introduce other issues sometimes. But, generally speaking newer is better.
That's where I'd start if I decided it was worth making the changes.
No warranty implied, yadda yadda yadda.
Also check into the stuff mir mentioned. If your new card supports a higher mode of anti-aliasing or ansiotropic filtering and they're enabled by default, that could cause it.
Wiley.
