Need a suggestion....

Ok,
I own a mesa boogie diesel 4x10 thats about 5-8 years old....somewhere in that range. And it can handle 600 watts RMS, it's front ported....(8 ohm cab).
I was going to buy the carvin RL600, and a mesa 1x15(found one cheap online), but i just bought what the guy said was an rl600 on ebay, but he sent me a pro bass 500 amp. He allready cashed and spent the 350.oo bucks i spent on it.(htinking it was an rl600 of course), so now i am in the process of getting my money back, or selling the amp locally, and having him pay the difference between what i get for the amp, and 350 dollars. But upon plugging this amp into my mesa cab(it was getting 500 watts into the cab), I realised that this cabinet has great punchy and solid lows.(Lotsa BALLS!) and cuts through very well. So now i am insearch of a new head for around 550 that I can use with just the 4x10. What can i get that will bridge or somehow give me a bit more wattage into one 8 ohm cab? I am pretty much looking for a head setup only.(A power amp/pre-amp setup would prolly cost too much for me right now) But i guess i am open to any suggestions. Also, I will not buy online, only used shops, or direct from the store or factory. Also, does anyone know anything about the pro bass 500 bass head made by carvin? How much should i be looking to get for it? It's in great condition, just isnt what I WANT for what i play and the sound i need. Plus a bit more headroom would be nice....

Thanks
Graham

P.S...I just saw a band play venue of like 2 thousand people with the bassist using only a SWR goliath III and a eden traveler plus. Obviously he had a PA, but their band has 2 guitarists(one has a 4x12, and one had a 3x12 setup), one drummer, one percussionist, and a keyboard player.....Should a 4x10 be plenty for my 2-3 hundred people and less venues?