I asked this a page ago, but it kind of got missed, or maybe there aren't UK gaffers perusing this thread. Anyway, would a budget of £500 be enough to build a gaming PC to run the likes of Skyrim at 1080p/60fps and run PS2/Wii games at full speed in 1080p? I've already got a SSD I can move over, so that'll save me a few quid.
You can try mix-matching parts from the Standard and Enhanced builds in the OP, just take into account that if you want PS2/Wii emulation you cannot skim in CPU, a Z77 mobo and heatsink for overclocking. An i5 3570K overclocked all the way up to 4.4GHz with a mere Asrock Z77 Pro3 (or Pro4-M if you want to go micro-ATX) mobo will take you a long, long way. That board in particular is dirt cheap and overclocks like a champ (which is great for emus) just changing the multiplier value in BIOS, and you'd probably be able to juice it up to 4.6GHz with a good custom profile.