How large is the room? Not knowing your basement size, I'll assume it's larger rather than smaller. I wouldn't mess with the Dynamo 300's, especially for home theater. Get one good sub and place it in the best location. Then get another one later on and put it in the other hot spot. Is $500 your max budget?
Subs>RBH I-12e, I-12. HSU VTF-15H mk2. Monolith THX 12(x2), THX 10(x2). XTZ 1X12. SVS PB-1000(x2). Speakers>JBL Studio 270/235c/230/225c. Sony CS3/CS8/CS5. QA 3020i/3090Ci, 2020i/2000c. Monolith Cinema 5bs. Polk RTiA1/CSiA4. Other Audio>Sony MDR-Z7m2,V6, XB900n,700,XB32,XB31. Sennheiser HD58X,HD4.50,PC37X. HiFiMAN HE4XX. Philips SHP9500. SIVGA SV004. SA HDTwo. HyperX CloudPS4. TB Elite AtlasAero. LG FH6,RK8,RK7,PK5. HK Onyx Studio4(x2).