I wouldnt upgrade to SB if budget meant I had to get a mediocre system. In a short while, Sandy Bridge wont look as awesome as it does now.
A Q9650 still holds its own in gaming. Its all the extra crap that it lacks but sheer clock for clock gaming performance is still very good.
2011 is the year of several awesome releases, first we get Sandy Bridge, then AMD FX Bulldozer cpus for AM3 and then we get Ivy Bridge LGA2011. If I didnt have the money to go full bore right now, having a system similar to ElAurens(which I do lol), saving up a bit for a full bore upgrade that lasts another two three years is the way to go. IMHO!