I have an Denon x4000 receiver and I just received my Epic 80-500 speakers. There was a problem with the EP500 sub so I'm being sent a replacement EP 500 amplifier which should arrive this week. In the mean time I'm without LFE output.

I have a concern. I was expecting a more robust mid to low range punch from the M80s. I've also observed that the sound level doesn't pick up until I hit the -15 - 0 dB range. Could the Denon receiver be underpowered? Will the sub, once I recieve it, fill in the mid -> low range as I had expected from the m80s alone? I have to say I'm a little underwhelmed at present.
Would a separate amplifier make a noticeable improvement to mid-low end punch and overall volume?