Unfortunately, your space requirements are very limiting.
If you could squeeze out a few more inches, the JBL S38 was a fabulous small speaker. It was designed to be positioned on its side, making it ideal for a bookshelf. It was also front ported, which helps a lot. As a bonus, it had great bass extension...down to around 45 Hz or so, and was decently efficient. It sold for around $500 or so a pair back around 2000 and was versatile and could really rock if called on to do so. It really would be ideal, provided you could find a pair on the used market.
The Bose 301 fits your space requirements almost exactly. You'll be giving up a lot of the resolution and audiophile qualities of the JBLs, but the current 301 is surprisingly good on a bookshelf. I tried it myself. It delivers a nice, spacious sound and actually has a ton of slam...where other small speakers compress under pressure, the 301 just keeps pumping out louder and louder volume, which would be good considering your musical tastes. Don't rule it out.
Finally, if you can fit a small sub somewhere, the sub/sat systems from Orb Audio (www.orbaudio.com) more than meet your space requirements and are very, very fine products and extremely versatile. You won't need a lot of power since the sub will do the heavy lifting, and the small size of the round sats will leave you room to spare. Plus, you can order them in multiple configurations, allowing you to use one per channel or two per channel.
If you could squeeze out a few more inches, the JBL S38 was a fabulous small speaker. It was designed to be positioned on its side, making it ideal for a bookshelf. It was also front ported, which helps a lot. As a bonus, it had great bass extension...down to around 45 Hz or so, and was decently efficient. It sold for around $500 or so a pair back around 2000 and was versatile and could really rock if called on to do so. It really would be ideal, provided you could find a pair on the used market.
The Bose 301 fits your space requirements almost exactly. You'll be giving up a lot of the resolution and audiophile qualities of the JBLs, but the current 301 is surprisingly good on a bookshelf. I tried it myself. It delivers a nice, spacious sound and actually has a ton of slam...where other small speakers compress under pressure, the 301 just keeps pumping out louder and louder volume, which would be good considering your musical tastes. Don't rule it out.
Finally, if you can fit a small sub somewhere, the sub/sat systems from Orb Audio (www.orbaudio.com) more than meet your space requirements and are very, very fine products and extremely versatile. You won't need a lot of power since the sub will do the heavy lifting, and the small size of the round sats will leave you room to spare. Plus, you can order them in multiple configurations, allowing you to use one per channel or two per channel.