If you're looking for the reliability and strong sound graphite can give you, consider a 4 or 5 string Modulus Genesis. The neck is built with a graphite spar inside that bears all the weight. Maple or other woods are fitted around the graphite to give the neck its shape. I've got a Genesis neck on a Frankenbass I made and it's great:
1. Not as "clanky" as a straight graphite neck
2. (see above) Has a woodier tone, but all the good things about graphite - even tone production across the board, endless bass fundamental, perfect (really perfect) intonation, never goes out of tune
3. Built like a brick sh*thouse. Beautiful fit and finish, great fretwork, super fast action.
Genesis basses typically go for a few hundred less used than Quantums. Harmony Central is full of great reviews. I've never talked to an owner who didn't love his. But I'd be curious if anyone out there who's tried or owned one found a significant fault.
Good luck with your upgrade. (SRs are good too, and maybe a little closer to the sound you've been getting.)