I'm torn between the two. Both portable and cost the same. I like the MB1215 speaker configuration, but is gonna be loud enough for ''most'' situations? But I like the expandability of the RB510 for later on down the road.
I'm playing straight forward Rockabilly with an M1, Super Silver strings and a k&k RAB pickup. ...small to med gigs... $600 is a nice price tag and is right about where my budget ends.
http://www.carvinguitars.com/products/MB1215
http://www.carvinguitars.com/products/BR510
thanx. and I'm all for other suggestions in that price range.

ok. Maybe I should have posted this question in the ''newbie'' or ''rockabilly'' forums? I think I made up my mind on my own. Still I am open to suggestions.
Thanx!!!

I have no experience with Carvin products, but at first glance, I'd be more interested in the flexibility of the 1215...quieter gigs you can just lug the combo, bring the 15 for louder. I would imagine you'd be better off with a 12 and 15 than 2x10 for rockabilly stuff, too. Seems like you get more for your $600 with the 1215 package.

Thanx for the response! yeah I do like 1215 idea too. My main concern I suppose is running out of head room with only 250 watts as opposed to 500. and I do like the graphic eq on the RB series...
I have owned Carvin Guitar amps in the past and have been very happy with em. just never owned any of their bass gear.

I picked up the little MB10 last fall. I had several Christmas gigs with a piano player friend of mine and wanted something really small and portable just for those duo gigs. While I was at the store down in Santa Ana, I tried out the MB12 and was very impressed. Larger than what I was looking for but much nicer sound than the 10" version. I don't think you could go wrong with either, but that MB series sure is nice.

Thanx Nate74,
it's tough because I don't live anywhere near a Carvin dealer and reviews are slim on most of their gear. Ive owned and played bass guitar through lotsa amps so I am familiar with quite a few rigs and configurations. However amplifying my upright is a whole new world to me.

I have the Carvin mb15/15. Sounds great with my fretless u-bass and my fdeck2. Can't speak about it with an upright though. Its definitely better with the extension speaker, so the mb12/15 would probably work fine for your needs.