Sorry to keep bombarding you all with questions, but, in the words of Chief Wiggum, "... it's the only way I'll learn." I've noticed that the Mesa M-Pulse 600 has 2 preamp tubes, while the Big Block 750 has 4, as does the Aguilar DB750, both of which are purported to sound "tubier" than the M-Pulse 600. Then there's the Ampeg SVT-6 PRO with *six* tubes in its preamp and driver sections. Is the number of tubes in the preamp/driver proportional to how close a hybrid head approximates an all-tube head's tone? Thanks for your input, everyone. Peace!