If you like the MB200 you will REALLY like the MB500. It has the same great sound and is just a little larger, but with much more power. The price is $400 plus shipping. Here's the description and specs from the web:
Weighing in at fewer than 4 lb. and taking up less than one rackspace, the MB500 delivers 500W of signature GK tone in a sleek, compact, modern head. Boasting GK's legendary 4-band active EQ and contour control, the MB500 lets you tweak your tone to perfection before hitting the digital power section.
In addition to its generous tone-shaping capabilities, the preamp section has a footswitchable boost channel with independent volume control to dial in just the right amount of grind and level boost when needed.
The MB500 is stage- and studio-ready with an XLR direct out with pre-/post-EQ selector and ground lift. Also offers a tuner out with mute, FX loop, headphone/line out, and dual Speakon outputs.
500 watts at 4 ohms or 350 watts at 8 ohms
4-band active EQ with variable contour
Effects loop and tuner output with mute
1/4" headphone/line output
XLR output (pre/post EQ and ground-lift switch)
Boost control (footswitchable)
2 speakON outputs
'69 Emmons P/P, '73 Emmons P/P, MSA Millennium, Legend, and Studio Pro, Reese's restored Universal Direction guitar, the MSA Classic plexiglass steel, as well as several older MSAs, and a bunch of amps, new and old.