Assist with Box Design

So i had an old Cerwin Vega 10" powered sub for the last 19 years i uss it to watch movies in my living room. Amp smoked a couple weeks ago and i have set off on looking for a replacement. With cost of new powered subs being so high I have decided to use what i have here. All i would have to purchase is the MDF. Fairly cheap if it will work.

This is going in a room 24x17x17, very high ceilings. I have a 2 channel 150 watt amp. I am planning on using 2 Rockford Fosgate RFZ 3812 12" speakers. Currently using this setup in 2.2cuft sealed box. its a bit boomy in the high end and drops quickly. Speakers and the amp are out of old system. I have modeled boxes in Box Pro and Winisd. Looking at around 6cuft box 19-20hz tuning. Cone excursion goes out the window. I can reduce the box to 3-4 cuft. All kind of blurs together after a while. Looking for a sanity check. Is it even worth building a box for these speakers? If i can get by with the box for now in 6cuft plan is to replace the speakers with some 15" down the road, when/if these speakers give out.
Speaker specs are
Diameter 12"
Magnet Weight 30
Frequency 25-200
Nominal Imp 8
RE 7.9
FS 25
Qts .61
Qes .7
Qms 5.54
SD 84 in^2
Vas 6ft^3
Cms 4.19E-04
Mms 3.35oz
VC Diameter 1.5
VC Inductance 5.38mH
BL 13.5
Xmax .3
SPL 88
PE 150 RMS/400W PEak