I've had my GK 400RB 210 combo for a little while and wanted to add a second cab to it. So yesterday a hartke 2.5XL found its way into my house. Some people think the aluminum cones sound too brittle, but I disagree. The 2.5 compliments the GK very well, the GK is a bit midrangey and the 2.5 adds a nice scouped crisp sound to it, great for slap. Perhaps I will post some miked sound clips and pics soon.