I have installed stereos in my own cars for about 15 years. The factory leads have always been sufficient for what ever I wanted to do. In fact I had a Jeep Wrangler with a PPI A600 running 4 Kicker 10'*, with a Kicker Impulse 350i running my mids and highs and had no problems with the wiring.
The only time I did have to use a relay was with a 89 GMC Jimmy. I had a Clarion 8571 with the same PPI A600 running two punch 12'* and a Phoenix Gold 1 farad cap. When I installed a clarion EQ, it kept popping fuses, I went to my installer and he wired up a relay for me, never had any more problems.
I can understand why you would recommend running a relay if It is a fairly large system, but why run a separate 12 volt constant, and on a entry level head??
02 Se with a few mods,
Coming Soon 1.9'* OR pushrods and other stuff