Sorry to join the topic a little late but I don't get nearly as much time to log on as I'd like.
Being from North of the 49th I admit a bias here, but for the money (at almost any reasonable price point) you really can't beat made-in-Canada speakers. So if I were buying a sub new, I'd look for Paradigm, Mirage, Energy, psb, etc, especially at the lower price points.
That being said, I'm also very impressed with just about anything that Definitive Technologies has done. They'd get serious consideration at mid- to mid-high price levels.
And when the cost starts to get up into the high levels, top-of-the-line Velodynes are hard to beat.
As to the original question, I've not heard the B&W ASW300s but I bought a used (2-3 year old) ASW1000 on Boxing Day and it is a very good performer. In fact I use it in my main theatre with a 12 year old Velodyne Servo 1200, and a passive home-built (using Polk drivers) and while the Velodyne goes much lower, on most material at reasonable (but realistic) levels, the B&W holds its own.
Both the Velodyne and the B&W would probably be a bit too pricey new, but at $300CDN (~$200US) and $325CDN respectively used, I count them as two of the best value buys that I have ever come across. More so since both were bought from terrific local speacialty shops that had taken them in on trade - and gave a 90 day warranty on them as well.
If you ever get the chance to be in Ottawa for boxing day sales, you will find some incredible deals (on more than just speakers) at any one of Stereo Plus, Audio Centre, and Audio Shop. In fact there's great deals to be had all year long. (My only vested interest is that I buy gear from all three.)
Jeff
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Jeff Mackwood