Oh, well. I've been a GK MB150 fan for yonks (a 'yonk' is about ten years). Not too expensive (about £1,000 for the complete set-up: combo plus extension cab), light (about 30 pounds), small, good sound.
However, I've just retired it. Replaced it with a stonking great Trace Elliot 1 x 15 500W combo. Yes. 500W. Weighs about as much as a blue whale. If possible, my wife hates its presence in my life even more than the GK combo.
The reason(s) are simple: this is the second GK combo that I've had. The first blew a transistor and GK couldn't have cared less. Eventually an amp tech fixed it, but I could never trust it after that. This one began to rattle. I tightened every screw I could find, and took it to an amp tech for a speaker check - no problems there - but still rattling away like mad. I play in a jazz orchestra - not exactly the loudest band in the world - and the little GK stack was always cranking away at about 90% just to keep up. OK through a PA, but really only just good enough for even moderate volumes. Quite hopeless in the soul band.
The Trace Elliot is just magnificent. I'm not quite so happy with the tone without a lot of modification from all those sliders, but the amp has loads of 'headroom'. I've never got the volume control above '2'. Lifting it is likely to cause a double inguinal eventually, but the conclusion is this: you just can't beat all that extra mass and that whacking great speaker, or the brilliant amp technology. It sounds great, it is reliable, it is loud enough (and it was cheap because I got it second-hand nearly new). If you're seriously thinking about lightweight gear do a few checks about longevity first, or resign yourself to only playing at low to moderate volumes.
If you want advice: go and listen to a few amps in the shop. Make sure that you hear them at the volume you want to play at. Check the online reviews beforehand. Stick with a tried and trusted name if you think you might upgrade it later - it's much easier to sell old high-quality gear than stuff that nobody's ever heard of.
best,