I've installed quite a few systems...and I've learned two things:
1. Not all amp-remote drains are the same
2. It is a pain to fix once the head unit remote goes.
I've had them give out on as little as two amps. On my last system, I had 5 JBL amps w/no relay (Kenwood head unit). However, I installed one after one season (just to be safe).
A Bosch relay is around $7 and 5 minutes to wire...cheap insurance, IMIO (in my ignorant opinion).