In real terms, quad-threaded applications are thin on the ground and will be until at least this winter. So, in most cases, this keeps a more or less even pace with its dual-core equivalent the E6600.
But in terms of a re-encode/compress test and Stalker at 800 x 600, and it's quite apparent what two extra cores can do.
If a loving parent/festive myth figure/lottery win gave you a couple of hundred sterling more for your PC-building fund than expected then, well, it's a reasonable price for decent future-proofing.
If not, get the E4300 for now and blow the savings on an 8800 or sit on 'em until cheaper quads appear on the market.