i believe hifonics are a little underrated, but not by much. they are very clean amps. put out very nice power. they aren't like JBL where the sole purpose is to send lots of power. they send very clean power. i have a hifonics zeus zx6400 for sale. it is 85x4 at 4 ohms, 170x4 at 2 ohms, 350x2 @ 4 ohms bridged. so you could send your dual 4 ohm sub 700 watts with this amp. it does have a subsonic filter and it is for sale. i need an amp that runs at 1 ohm. only been used for a couple weeks. its the 20th anniversary edition. let me know if your interested. asking for under $200.
EDIT: didn't notice you were running 2 subs until after i posted. this amp would be good for one of the subs...wouldnt work with both of them. but still let me know if you are interested for some odd reason //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif