OK, the amp is not what is efficient, the speakers are where efficiency matters. If the amp delivers 200 watts, that's what you get, 200 watts, it doesn't matter if the cab handles 200 or 2000. The wattage rating of the cab is how much power it can handle, it will only put out what you put into it, in this case, 200 watts. If you're into rock/punk etc, a 2-10 cab by itself will probably be lacking some, they sound good when stacked with a 15. Try looking at some 2-12's or 4-10's. Eminence is one of the biggest speaker manufacturers out there, they supply speakers to companies to put them in their cabs. Cabs of many different names may have eminence speakers in them. Peavey is good gear, can usually be had for low prices and is very reliable but maybe not as clear or modern sounding as some of the more expensive stuff, they are known for being ballsy, loud and reliable. Don't know what your price range is but look up Ashdown MAG300 and Avatar speakers, either a 212 or a 410. This setup can be had brand new for about $700, sounds great, you will not have to upgrade for quite some time. If that's too much money, look at the used market. If you end up getting 2 cabs, make sure they are both 8ohm cabs. Combined they will make a 4ohm load which is safe to run on about any amplifier you end up with. Search the FAQ's for ohms, they matter, too low of an ohm rating will let too much electricity come through your amp and fry it. Whatever you end up with will sound awesome compared to your practice amp. When you say you need a rig for small gigs 300 or under, is that $300 or 300 people? For $300 dollars you can get a 150-200 watt combo amp with a 15" speaker in it, will sound good and handle playing small bars, parties, etc. or maybe something bigger when buying used.