Well AM3 should be on for a while at least, the i5 and i7 systems are simply overkill and money wasted in my opinion, you could get a mid range AM3 system + a high-mid end graphics card for the price of an i5/i7 system without a graphics card easily. Also i5 and i7 systems are very picky about memory, not too familiar but they require low voltage stuff whereas AM3 can use both. i7 then also runs best when there's triple memory kits and those aren't exactly great in terms of pricing.
Also, I know the guys around here don't like the idea of eBay but for £50 or so nowadays you can grab a 8800GT variant, sometimes if you're lucky then you could perhaps even grab an 8800GTX 768mb for £50. However obviously the warranty purposes and shady dealers makes it a less attractive choice. 8800GT maybe be one of the oldest cards around but it's performance is still good enough for pretty much every game to be able to run on max settings provided your resolution isn't too massive.
4770s were only £55.35 and £58.00 at a point and
IIRC 4850s weren't much more either. However, like I said before, unfortunately you don't have that chance anymore (and sadly me neither, would have loved a 4770 for crossfire though I do need to ask myself for what purpose as with a single 4770 I can run everything at max settings (apart from Crysis in terms of AA). )
I'm not saying the 4670 is bad but the next thing you'll want to upgrade would definitely be that so it seems a bit pointless to me to be honest. It's like when I thought back to myself, I got an 8600GT for £40 in 2008 cos it was within my budget but now I simply see it as £40 wasted.
But if you spend a life waiting for technology to get better and prices to drop then you never get anywhere haha.
Hope that gave you some ideas on what you personally want to do, everyone is entitled to their own opinions and actions.