Tonyangel,
I'm using a ClassD Audio SDS440CS amp to drive a pair of Magnepan 2.7qr spkrs. I bought it to replace my older Aragon 4004 class A/B amp that is similar to your 2004. I could not be happier with this amp. It was only $630 and puts out a solid 440 watts @4 ohms and it is very good from top to bottom. I think the CDA designer, Tom Ross, is using some proprietary design that allows this amp to handle low impedance loads. This amp doubles its power when going from 8 ohm to 4 ohm loads, which is unusual for a class D amp at such a budget price. This doubling of power, when the impedance is halved, is typically considered a good indication of a robust power supply in an amp's design.
I would recommend pairing the amp with a tube preamp if you want an organic sounding system with natural bloom and warmth. But, if you prefer a more neutral and accurate presentation, I'd use a solid-state preamp or an ARC tube preamp. From my experience, and from reviews and blogs from users I've read, the CDA amps seem to all have a neutral and accurate sound quality.
I've been using the SDS440, 60% for ht/40% 2-channel music, for the past 5-6 months and thoroughly enjoy this amp for both.
Because your Silverlines are somewhat inefficient, as my spkrs are, I would advise you to consider trying the SDS-440 or the more powerful SDS-470. I can say with confidence that you'll be able to get very good sq even at volumes louder than you'd ever care to listen without distortion, compression and without the amp getting more than merely warm to the touch.
If you decide to give one a try it won't be a big financial risk. CDA offers a 3 week trial period and you'll just be out shipping costs if you decide to return it.
Good luck and please keep us informed.
Thanks,
Tim