this, if your not careful you could spend triple for less performance, if you want something better then 305's best to build your own. http://www.diysoundgroup.com/featured-for-mg04a00409/speedster-kit.html
But doing this means you now need a decent amp too ~200$ more. The JBL's have integrated amp, they are actually biamped, with an amp for the low's and and an amp for the high's. You could use a cheap t-amp, but for something like a Speedster, that's almost criminal. Need a good, entry level A/B amp. The cheapest i'd recomend is a parts express 75 watt per channel amp(Dayton APA150, 160$) . But the Emotiva A100 (229$) is probably worth the extra cash for an excellent budget choice. Either way, now we are talking about a pair of speakers and a relativly large, hot A/B amp. Alot less "Clean" then a headphone amp/dac/pre combo with a pair of JBL's. (or other powered monitor)