The tech guy is wrong - at least about the PCI-E part. PCI-E 1.0 x16 is about the same bandwidth as PCI-E 2.0 x8, very few modern graphics cards can saturate that bandwidth. Given the price range of your GPU/PSU upgrade I highly doubt you will run into any interface bottlenecks.
If anything might bottlenecking your system, it *might* be the platform. (I'm guessing it's the rig in your signature) But even then it's not a huge deal and further overclocking will alleviate it quite a bit. However I could be wrong depending on what your new GPU is.
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