Make Iridium Tools the same strength and speed as Iron (Thus no obsidian), but last forever and you have semi-balance.
It would also balance with the Mining Laser+AMGIRIDIAMDAGGER combo, if Al makes it Iron strength.
To make something last forever, you have to give something up- Strength and Speed. Faster then a Mining Drill is just too OP.
Obviously, the metals would be too dense for enchants- Some magic mumbo-jumbo that IC2 Technicians don't care about.
On that note- EU Limiter Cable (or, a block just called 'EU Manager') is a nice idea. Maybe have it manage both packet sizes (thus, if made expensive enough, can work as any kind of transformer, even EV->LV, or LV->EV), and manage the amount of EU allowed through it.