So as much as I'd like an i7 for the sake of having one it certainly seems like it would be an unnecessary waste of money and I would benefit more from an i5 + SSD rather than i7 + non-SSD.
On the subject of "enough".. lets look at it with
the PassMark rankings.
The laptop I use at home uses the Athlon X2 QL-65 (2.1GHz, 2 Cores), which has a PassMark of 1084.. it does feel noticably sluggish now and I think there's too much stress on the HDDs too.
This comp at work uses the Core 2 Duo E7500 (2.93GHz, 2 Cores), which has a PassMark of 2005, is slow with Premiere when I had to use it briefly, but I don't stress it as much as the laptop at home anyway so it's hard to tell how quick the machine is (the x264 benchmark gives a good idea encode-wise though)
The Core i5 760 (2.8GHz, 4 Cores) has a PassMark of 4604, and even without an overclock I realize that should be more than enough for me. The overclocking is just something I've wanted to have a go at for a long time now, so if I overclocked it (which I should be able to significantly with the Titan Fenrir) then I'm sure it'll be more than I ever need.
As far as 3D performance is concerned, I had to play Modern Warfare 2 on a low-res to play smoothly, AudioSurf on "Premium" graphics mode is laggy, CounterStrike Source is always jumpy when spoon goes down = I die more often than I should be - and this ATI Mobility Radeon HD 4530 has a G3D PassMark of 259.
The planned card is an XFX ATI Radeon HD 5770 (though I did want Nvidia this card seems like the most reasonable one to get at the moment, especially at the price it's at right now) - with all the features I could possibly want and a G3D PassMark of 1567.. well.. I think that should be more than enough!
Seems like, then, I should go for the i5.