I have a suggestion as well: You might consider the Communications Concepts Inc. (CCI) model EB-63 amplifier kit. It's great "bang for the buck," costing only about $100 or so including the amplifier printed circuit board, a kit of all the electronic parts, and complete instructions. This is not a "Heathkit" type kit, where all you need to know is the English language, it's a bit more difficult than that. It's based on a Motorola engineering bulletin (#EB-63, hence the model name) and it works very well. 5W drive produces about 100W output (possibly more) on 3.5 through 30 MHz bands. The kit is not complete, to the extent that you have to supply your own chassis and heatsink, and maybe some other easy-to-find components (on/off switch; cooling fan, if necessary; in-line fuseholder -- stuff like that), which frankly are all at Radio Shack. I built one back in 1989, and it's been plugging along reliably for the past 12 years with zero problems or failures. It probably does NOT meet the spectral purity requirements for HF commercial equipment, without adding output filtering; however, I've found it is extremely clean when operated in its LINEAR range (not in compression!), and that does extend up to about 100W output power. And the cost is hard to beat. Also, if you build it yourself, you'll definitely know how to service it, should that requirement ever occur. I've been using mine mobile/portable for years, never a problem, never a complaint. It draws about 15A peak at 13.8Vdc for 100W output power. Good luck!