Originally Posted by
Aussie Mark
Thanks Rhys for the extra info. A good 4x10" cabinet should be perfect for your needs, so if I were you I'd be on the lookout for a used SWR Goliath or Eden 4x10, which will set you back around AUD$1200.
That leaves you another $1300-1800 for more power, so a preamp/poweramp rack would be the way to go. You can score a decent used power amp putting out 600-1000 watts in bridged mono mode for around $1000 (eg. Yamaha, Crown, Australian Monitor, Perreaux, Peak), or you can buy a new Chinese made power amp for under $1000 (eg. Phonic, Behringer, Alto, Crest).
For preamps, you can spend anything from $250 (Behringer tube mic preamp, great value for the money) to $800 (used Demeter or Alembic from ebay US or Bass NW, new Sansamp rackmount pre). In between, there are used preamps like the Yamaha PB-1, Roland SIP-300, Blue Tube, ART etc).
There's nothing wrong with your current rig other than I suspect you're running out of headroom. Some more power should fix that for you and allow you to get the sound you want from your MM basses.