That sounds pretty fair price for a Mk IIb, depending on the condition & features. Is it a 60/100 watter or just a 60 watt? Does it have reverb? Tolex or hardwood cabinet?. Combo or head?....The Mk IIC+ is considered the creme de la creme of the Mk series, but there's some good tones to be had on the Mk IIb ..
The rhthym channel sounds really good when set for clean, very Fender Blackface-ish. The lead channel's voicing is simular to the MK I's: Think Santana! My Mk IIb lacks the on-board 5-band Eq, & it has gobs of midrange & highs, but with the EQ, I'm sure you can tame the mids if you so desire....
In a nutshell, the Mk IIb is a great amp for country, blues, classic rock & maybe even some types of alternative rock. It doesn't do metal very well: The MK IIC+'s, Mk III's & Mk IV's are better suited for metal...