I mentioned in another thread how much I am loving my Greenboy designed fEarless cabinet for bass. I also love it for guitar too. It's a 3-way FRFR 1x12 that I built for about $650. It handles 533W without sweating.
fEarless is the DIY solution, but there is also a commercial line called fEarful:
[Blocked Image: http://greenboy.us/FEARLESSComp.png]
The commercial stuff starts at around $1000, but it might also replace whatever you are using for guitar too. My 1x12 keeps up with a very loud band on both bass and guitar. SUPER deep for bass.
Here's an update on my experience with the fEarless cabinet: Fantastic for bass and great for clean guitar. After living with it a while longer, I'd say it's good for distorted guitar, but there might be better solutions out there. When the volume of distorted guitar is cranked, it tends to get a little harsh with the three way configuration I used. At lower volumes, it still sounds great on all sources.
I'm in a similar situation and need a small bass cab. Would a Yamaha DXR 12 get me there ?
Regarding my fEarless build, I might have made a mistake in my crossover. I'm in contact with one of the designers who is still helping me sort it out, so I am retracting my retraction for now. 
Hey Geese, how much are you looking to spend? Shoot me a PM, I might have an idea for you.
Old Crow, I'd probably stay away from most PA cabs for bass. They generally use mid-bass drivers to go "lowish" and rely on subs for getting down to true bass frequencies. Yamaha quotes 52Hz, but that is at -10dB. I just purchased a 12" Barefaced full range cab to replace my fEarless and it bottoms our at 30Hz, and that's at -3dB or -6dB down IIRC. These new high excursion bass drivers are making 12" speakers do what 15" or even 18" speakers used to be required to do. Depth is a function of both speaker area and excursion. Increase excursion and you can decrease the area to get equal low-end performance. They are very expensive though, and usually are only used in high-end bass cabs or subs. It's for this reason that I was looking for a high-end bass cab that was also full-range, rather than looking for a PA cab. I want a bass cab that works for guitar too, not a guitar/PA cab that sort-of works for bass.
A PA speaker will work of course and probably sound great, but just don't expect deep lows.
