Trouble with ep4000

I'm sure I'm doing something stupid here. I got this ep4000 to power 2 15" dayton hf's. I haven't ordered the dayton's yet, but I'm testing it out on a pair of old sony xplod 12"s I had sitting in the basement. I know they work, I hooked them up in the car to check. Here's how I'm hooked up:

RCA splitter from sub out > RCA to TRS > channel 1 and 2 on amp.

Then I have the speakers hooked up to the pos and negs on both channels of the amp. The 30hz crossover is set on both speakers, and the clip limiter is on for both speakers.

What am I doing wrong? It seems so simple.

Edit: I should also mention I tried to hook it up to one sub without the rca splitter to get rid of that variable.

So If I put it in mono and plug both TRS's into the amp, turn both channels on the amp all of the way up, and turn the subwoofer level on the reciever all of the way up, I get sound. Long sentence :P

With everything cranked I get a reasonable level out of the subwoofers, almost perfect actually. I wouldn't want to go any higher. The only explaination that I can come up with is that the receiver just can't send a strong enough signal to the ep4000. I'm using a YAMAHA RX-V371. So my problem is solved for now, hopefully it can send a strong enough signal to the daytons when I get them.

I realize I kind of solved my own problem, but does anyone have an opinion on this?