Well in my experiments with up to 5 gain stages in front of the splitter (if you count the splitter driver- otherwise its four stages and a driver-splitter ), is that the more overdriven the pre-amp is, the more bass you have to get out of it for it to sound any good (smaller coupling caps and cathode bypass caps - Marshally values). Also the more unstable the amp becomes in terms of weird oscillations etc. This can be overcome by lots in inter-stage padding (voltage dividers and tone shaping RC networks). Check out some of the AX84 lead pre-amps. But its a fine line you walk and to design it properly you really need to work out all the variables (such as how you are biasing the stages, the miller capacitance of each stage, the input and output impedances of each stage, etc) in theory first. So go and read up on some articles about the basics of gain stages - at Aiken, or the Valve Wizard, and others.