You might want to do a search, I'm sure it's been discussed before. Also, search the
diyAudio.com - audio projects by fanatics, for fanatics forums, a lot of good info there too. From what I gather upgrading to faster opamps can create problems such as oscillations and exceeding the power supply current capacity, although 5532's are already pretty current hugry. Oscillations can be a problem even with bypass capacitors because of parasitic capacitances, especially if you add sockets to a originally unsocketed design. 5532's are bipolar-based, so I guess it makes sense to use bipolars for upgrades. There's also the issue of offset voltages, if the opamps are directly coupled to the next stages. These offsets keep adding up in subsequent stages (and gain multiplied) robbing headroom (by raising the dc level), but shouldn't be an issue if the stages are capacitor coupled. I am currently working on an 80's Souncraft 200B and I'm thinking about upgrading opamps too. Btw, is it ok to use regular contact cleaner to clean pots and faders? Maybe use lubricant afterwards? There's a member called Jim Williams that works on consoles hopefully he can chime in.