tuning subwoofer sound

Hello All, I have been trying for about 6 months to get my subwoofers dialed in but can not seem to get the results that I want. I feel like the I am not getting the best performance out of them. I also think that considering the amp that is pushing them and the make and model of the sub I should be getting more from them. Maybe I am wrong, that is for you to decide. This is what I have and how I have it set up now. Amp: Alpine MRP-M500 Subs: Two MTX TR55 single 4 ohm voice coil Subs are wired in parallel for a 2 ohm load Amp gain is set to approximately 3/4 full (I'm afraid to go any higher) bass boost is set at 6db. Sub box is .75 for each sub sealed. I have a parametric EQ on my radio (Pioneer DEHP2900MP) set at 80hz/2w with a +2 boost. I also have the bass boost on the radio set to +2 which is boosting frequencies below to crossover point which is set to 80hz. I also forgot to mention that the amp crossover is set between the 100 and 75 markings. Sorry for being so long winded. The problem is that the lower frequencies don't seem to be playing through very loud. The bass that does play through is very punchy and the overall bass is just not as loud as I though it would be. Do you guys have any suggestions. I do have some poly-fill in the box but not much. Maybe a volleyball size chunk for each sub. Just to let you know at this time rebuilding the sub box is not an option. Thanks for any help.2005 Honda Accord DX

well the subs that you are using are 400rms each and the amp that you have is 500rms @2ohms. so at 3/4 gain you are producing about 375rms roughly, assuming all wire and power inputs are sufficient. based on that, you are showing just under 190rms to each sub which is a little under half of what your subs are looking for. another thought, you may want to allow all the way down to 30-35Hz on the amp as well.35 Hertz custom car audio and automotive fabrication

First, use the head unit crossover or the sub amp crossover but not both.  If your head unit is set to 80Hz LP, then turn the crossover on the amp off if you can, or set it all the way up to its highest position.  Then kill all that boost and set your gain properly.  Here's how; https://www.the12volt.com/installbay/forum_posts.asp~TID~85479~PN~1.  Let me know when you've done that.Support the12volt.com

Thanks DYohn, I actually am using both but I am going to re-tune without using the radios crossover. I'll let you know how I make out.2005 Honda Accord DX