The chassis may also end up costing a much larger portion of the total cost than planned, look around for cheap metal supplies or find readymade chassis and buy them. Just make sure the heatsinks will fit somehow.
Here's a suggestion for chassis layout. The aluminum U-bar can be bought in standard (5 meter where I live) lengths and cut with a jig saw. I also found buying a long (1 meter) length of heat sink extrusion is cheaper than buying short pieces, it's easy to cut with a jig saw, remember oil during cutting for cooling the saw blades. Tapping threads for bolts into the aluminum simplifies assembly, it's time consuming, but worth it. Make sure to use aluminum thick enuff to handle the weight. A good solid chassis actually 'sounds' better because of better immunity to vibrations.
I recommend transistor packages like TOP-3 or similar that can be fastened directly to the heatsink without brackets which are needed for TO-3 packages.
Shielding the electrolytics from the heat is a very good idea, their efficiency is reduced by 30 to 50 % every 10 degrees celcius of temp increase. Mount and damp them to eliminate vibrations, caps are big time microphonic.
Placing the transformers and rectifiers on the front plate enables easy disassembly, but the wires to the first capacitors MUST be very short. Placing some capacitors next to the transformers and the rest close to the output stage is a good idea. That way the power supply is like a module that can be removed and worked on by simply removing the front plate. Mount the transformers with rubbermounts if possible. Test transformers for excessive hum before assembling, some are unexceptably noisy.
Allow more space than you think you need, nothing sucks more than to have to modify or fix something thats a bitch to get to because of tight spaces. Good space gives better air circulation as well.