Well have read and read and read I think I am ready to begin my install.

The car: 1997 Toyota Corolla DX - un-modified factory stereo
The plan: remove existing head unit, replacing with tunerless-Empeg feeding a 200w Kenwood amp and using existing speakers for now.

I spent Sunday afternoon poking around the car, with lots of staring at bits trying to figure out what will go where, what additional parts I need and so on, and I think I am ready to begin work, but just posting my plan here so other more experienced people can poke holes in it.

Interfacing with the car.
This I believe is the correct one for my car, and will give me a set of pigtails to solder to the pigtails on the Empeg ISO adapter. Question it also has speaker wires so presumably I solder the output from the Amp to this or is another connect method more suitable?

Powering the Amp.
On the same site I found this installation kit. As I plan to mount the Amp under the passenger seat and feed the power cable through the firewall just above the drivers feet via an un-used hole - is there anything else I need? I have found the nice wiring channel on the passenger side door sill - so the positive wire will be pretty hidden until it peaks through the carpet and runs under the seat. For the negative side I plan on using on of the seat mounting points.

Fitting the Empeg
Like other on this board have found, the Toyota radios are partially hidden behind part of fascia. Looking from the other side & playing with the sled I feel I have only a few millimeters to trim off - so no problem there. My fear is that I have no anchor point at the rear, so other then a few bent bits of metal at the front there is nothing supporting the unit. Is this okay? Or should I dig around behind the dash more and make use of that screw point on the rear of the sled?

Empeg to the Amp, and back.
Two pairs of RCA cable and a remote turn-on wire go down from the Empeg to the Amp, and four pairs of speaker wire return from the Amp to the car harness mentioned above. Is that it? Granted the awkward part of getting the cables in place and nicely hidden out of site is where experience comes into play, but I think I can run them inside the plastic cover that sits over the gear shifter & parking brake area, with just a little hole to allow them exit under the passenger seat.

Misc. questions
Anything flaming obvious that I have missed, that is a sign that I should fork over money to have a pro. do the job?
Should the connections between the two wiring pigtails be soldered or crimped, and what about where the speaker wire attach to the car harness? I'd prefer to overkill then to have to redo it all as I don't want to go behind the dash again except to add a tuner.
Finally, what are the wattage & size are the factory speakers in a Corolla? I believe the rears are ~5-1/4" and the fronts are 4" in size, but what wattage? I believe the are 4omhs. Just wondering if the 200watts the amp pushes out will blow them easily.

Quick PS: Has anyone dealt with partsexpress.com? Any problems? They look professional, but just want to be sure.