Thermalright heatsinks got progressively better, so I don't know why you've gone from looking at an SI-97 to an SLK700 vs an ALX800. The SI-97 is the one to get. Performance is only a couple degrees difference at most, but there's no question the SLK700 and ALX800 are at the bottom, then the SLK800 and 900, the SP97 and the SI-97 at the top (for Socket A). It's a marginal thing but if you're really interested in getting the best possible cooling, go with the SI-97. I don't know why there's any debate anyway. It's cheap, it's light and it's the best performer (for Socket A). And from what I've heard, because of it's design it's also quieter than the previous Thermalright heatsinks, but that's not a primary concern for you I suppose. Go with the SI-97 and slap on a Vantec Tornado. You won't regret it.