When adding a power supply - go with the most powerful one. It has been my experience that the older machines were under powered by the time 2CD's and 2HD's were configured in.

The difference, for me, between the 35.00 and 80.00 transformers has been, clearer CD burning, and no more computer crashes.

It is not difficult.

There is no need for a new tower.

Sincerely,
Gargoyle