If your buying a new HU my suggestion is dont be cheap! Just putting in good quality head unit to replace my stock unit i've had my audio sounding better then alot of my mates. The best bit is i spent a few hundred on my system... most of them spent $1500+... Rolla ftw! :D What wattage is that Sub btw? Be careful with what amp you get as well :) if you can try to stick to main stream brands unless someone can vouch for you that it'll work well :)
Pretty sure some people have managed to hook up the steering controls? is yours wired or IR?
haha putting in a new HU, Sub and Amp isnt that hard, all you need is the basic tools, plenty of spare time, someone to supply cuppa's and a handy diagram with the Toyota Wiring Diagrams
BUT!!!
Always disconect the - Terminal on your battery first as well....