Bass in the 300-600 range...

I have uncontrollable GAS. i just got my rick, i just got an SX, and i just got a 1x15, and all i ever spend my money on is bass stuff. i will be in control of 300-600 within the next month, and i was thinking of some stuff... just a new bass. I really am into fretless, and i'm into 6ers. what would be a good bass in this area? i'm considering new and used. i've been eying either the new Brice Fretless 5 and the Brice Fretted 6... (hell, maybe both!) I'm sure this has been done before... but eh. so if you guys have any ideas for me, please help out.

Peace,
Scott