Is my PSU affecting my performance?

It is possible that it affects the GPU by under-powering it and this is your issue but I suspect there is a bit more to it. You need to change the PSU to provide more in the way of a stable power supply, you need to look at the number of Amps as well as the watts provided. May I suggest you look at the Corsair Gamer series as value for money with excellent stability.

The GTX460 as you say is not the best of cards but it is far from poor, see if there are any options to overclock it and this will increase your frame rates.

You need to be sure your PC is also running well, so perhaps clean out the registry and de-frag the drive will also help the CPU and the HD to perform at their optimum as well.

If you don't have anything to do this then try Tuneup Utilities, don't use CCleaner, it is not always accurate or safe to use - I get dozens of PCs every month that fail to boot after cleaning with CCleaner.

You can find TUU here - http://www.tuneup-software.co.uk/download/

and use its 15 day fully function trial to clean up your PC and if you like it you can buy it.

Let's start off by giving you my specs (before I made some upgrades / overclocked)

AMD Phenom II x4 955

ASUS GeForce GTX 460 1gb 256bit

4gb DDR3 1600

Antec High Current 750w

I was running Skyrim maxed out @ around 60+FPS, and as you said, the FPS dropped a little bit in certain areas (~40FPS, still playable).

I was running Crysis 2 maxed out @ around 30-40FPS+, 60+ indoors.

Your FPS seems alright, actually. Try overclocking your GPU. I managed to hit 950Mhz (speeds as high as a GTX 470!).

Overclocked:

AMD Pheonom II x4 955 @ 3.8ghz

ASUS GeForce GTX 470 1gb 256bit 950/1900/1950

It gave me a great FPS boost of 10-20FPS+. None of this really matters anymore though, because I added a second GTX 460.

-Update your drivers

-And btw, your PSU does seem a bit low. My system was drawing around ~480w with one card (non overclocked). And your 975 should be drawing more. It might be a good idea to upgrade it, even if it doesn't give you a performance boost. Your PSU might actually blow out.

Your setup is not very high end, THe gtx 460 is a good card.. but its long outdated and hardly the best. You could most likely max everything out at a lower resolution such as 720p, but thats no fun. Your power supply is fine, your CPU and GPU are getting outdated, Not to mention the term MAX is such a lose term, most games have many options which can be cranked up such as sliders, however they boggle your system down with little to no visual quality increase. Now a days SLI and CF are the way to go for high end gaming.

the objective of a capacity grant is to grant adequate wattage to the contraptions so they could stay powered up. once you've too many contraptions and your PSU isn't solid adequate you'd be overloading it and putting further rigidity on the unit. this can reason it to both malfunction earlier than regularly occurring or might want to initiate a fireplace.