Pick up the most expensive 6.5" component speakers you can afford without spending more than $200 for the set. That or you could actually try to do a completely custom design, aka pick your own drivers. Try these sites:
Madisound Speaker Components | Assisting speaker builders for more than 25 years.
Parts-Express.com - Speakers, Speaker Building, Home Audio and Video, Pro Audio, Electronic Parts & Accessories PARTS EXPRESS, Speakers, Speaker Parts, Guitar speakers, Bass speakers, Woofers, Drivers, speaker upgrades and replacement speakers. Emine
www.mach5audio.com
Creative Sound Solutions - Loudspeakers, Parts and DIY Speaker Kits