best sub for spendor s8e and 2500 c feet room?

Any guidance on best sub for spendor s8e and 2500 c feet room? Cost less than $1.5k (new or 8/10+ when used)

I used an M&K MPS-350 with the S8e when I had them. High passing them with an M&K bass management controller improved their clarity a great deal. I also plugged the rear port, but I'm not sure if this was of much benefit.

If I was doing it today, I'd probably consider a pair of SVS SB12-Plus subs with builtin bass management. Otherwise, I'd pick up an NHT X2 filter, which supports 1 or 2 subs, and then pick just about any 12" sub from SVS, Hsu, Velodyne etc. There are a lot of really good subs available today and you don't have to spend a fortune to get one or two.
I use REL Stadium 2 and 3 with my SP-1s and S-100s. Cross them over at 22 Hz and drive them from the speaker terminals. Sounds great.
Think your best bet is a pair of subs in a room that large. Sorry to burst bubble & budget.
You can go with cheap subs if you don't push them to go down into the 20's. Set them to roll off at 36hz +- and they will work fine. Even expensive and big name subs can and often do sound bad at those low frequencies. Two less expensive subs should sound pretty good and will add a nice foundation.

My opinion here.....
If you are going to roll them off that high what is the use of having them? If you want real bass for low dollars look at the older passive Hsu subs that are [as of last night] listed at $350. They produce REAL bass at 20 Hz and are easy to drive. I have a pair, they are not fancy but have good performance. See old reviews in Stereophile and Audio Critic. They may now be on Ebay.
That is a great suggestion.. I forgot about the Hsu's. Heard them at the CES show a number of years ago and they sounded good.
Very helpful!! Thank you for the advice!