I used the Hartke 3500 in its 4x10 combo version for about 3 1/2 years, and always found it to be solid and reliable. I'm using the GK 1001-rb2 (big brother of the 700) now, and like it better. Easier to use, and a nicer tone, IMO. You won't be making a mistake, whichever you buy, but I'd pick the GK if I had to make the choice.
