Some time ago I would not have hesitated to recommend the C1 2.4 but as more time passes and fellow OC'rs continue to post there findings with their C1's I am not so sure C1 stepping has an OCing advantage over her B0 sister. So between the two cpu's you mentioned I would say go with the 2.53. This motivated me to add though, if you are trying to reach the 3gig barrier with the least amount of money you may have better luck with the 2.26. It seems to be the better OC'r than the 2.53, (I use the 2.26 myself and am currenly only bottlenecked by my memory...2.26 @ 2805, 165 fsb) and the 2.53 is a much more, 'hit and miss' chip when it comes to higher OC's. If your looking for a, 'guarantee 3 gig', (I hate that word -guarantee- when it comes to OCing) and have a little more money to spend I would say go with the 2.66 or 2.8. But we all don't -always- have $400-$500 sitting around, do we?
-out.