[quote name='Beer of the Bass' post='973104' date='Sep 30 2010, 07:45 PM']Cheers for the suggestions. The price of the Beta is definitely attractive compared to the 3015. So higher Qts is a desirable property in this situation? Is the Delta also worth looking at, or does the bigger Xmax of the Beta make it a better option?[/quote]
A high Qts is not desirable at all. On the contrary; it's what you get when you reduce the size of the magnet in an attempt to build a speaker as cheaply as possible. In your cabinet, the Beta will give you one-note bass centred on 100Hz with nothing below that. To see what I'm talking about, go and have a look at the cabinet suggestions for this driver on the Eminence site. The optimum cabinet size for this speaker is around 800 litres, which should tell you something.
When you try to get a little fatness out of your sound by boosting the fundamental, you will have very little power left to do anything else. Trace Elliot get away with that approach (the Trace Elliot contour), but their amps are more powerful than yours.
At the moment, the best specification 15" driver on the UK market is the Fane Sovereign Pro 15-500, which costs about £80. There is also the Fane 15-500, which is cheaper (£68) but doesn't have a cast chassis - which is worth the extra IMO. I know that you don't need the power handling, but high power handling is a characteristic of a good quality driver nowadays. Any of these drivers will be considerably heavier than your Celestion, by the way.
AFIAK, if you pay less than £70 for a new 15" driver it will have been built down to a price.
If you're not in a rush, you could keep your eyes open in the For Sale section here. Used 15" cabinets don't seem to retain their second-hand value as well as others, and there have been some real bargains on here lately for £100 and under.