not enough bass. What do i do?

I have 500 w rms mains and 500 w rms subs. My mains way outperform my subs. i built the subs myself using the highest recommended volume and 4 evenly distributed 4" ports on each tuned to 37 hz. I have my sub amp clipping but my mains can go much higher volume. I don't want to scrap my base cabinets because of the time and money i have in them but im thinking i should have built horn boxes instead. I use a crown 2500xls in stereo for my 4 ohm subs and 2 crown 1500xls one for each 8 ohm main bridged mono crossed over at 198hz. any sugestions?.

Are there 2 subs? and what drivers are they?

you could try swapping the amps i.e.

2500 stereo 8 ohm 440 per mid high cabinet
1500 mono 4 ohm on one sub 1550 watts
1500 mono 4 ohm on other sub 1550 watts

mid high cabs always sound louder than the subs with equal wattage.
*You should have plenty of power for the subs so use it as headroom ( less distortion) and try to keep your foot out of them lol
*you will be low on the wattage for the high end so if you have to run them hard the distortion you create will make it easier to blow them so you may have to get a different amp.

option 2 you could keep it the same and buy two more subs and run the 2500 at "2 ohm dual" for 600 watts each sub. easier and quicker would be try the first option. Also depends on what your needs are for total volume for the mains.

Add more sub's

Yes. They are Eminence Delta Pro-18C 18" Driver 4 Ohm.

cool. nice stuff. either swap amps or buy more is my initial stabb. Also is that a praise logo? good news?

Yes

Its Good Newz Band with a z. I see your photo is a bunch of speakers. Do you repair them or sell them ?

I landed those and sold all but 4 12's and 4 2" horns .... Making some long throws for my bands
Anxious for Nothing & Blues Healer