For my Eclipse I only use Autometer. But I am sure you can locate some on Ebay for much cheaper. Just remember, you get what you pay for. As far as the guages messing with the ECU, it shouldn't if you are only adding a sensor but not disconnecting the old one. On my Eclipse, she has, Boost guage, A/F ratio guage, Exhaust Gas Temperature guage, Oil pressure and water temp guages. All Autometer, Phantom Series. Also, my personal opinion is to stay away from the mechanical guages. I wouldn't want one of the lines to break inside the cab of the vehicle and you either have hot oil or hot anti-freeze spraying around. Just my personal opinion though.

Good luck.