You don't NEED to upgrade the amp, but you'd be amp limited.
I'm sure they'd still put out really good bass.
Unless you just absolutely love the boxes, it seems high to me. I guess it also depends what you value your time at.
As stated above, if you bought these brand new today.....
Inuke 3000dsp - $280
2 x SI HT18 - $320 ($160 each)
Optoma HD37 on 138" DIY AT Screen | Infinity Beta 40s, Infinity Beta C250, Atlantic Technologies 224 SR
DIY Alpine SWS-15 in Cyclops box (LTD02 ported design) | Old Pioneer VSX-521 | Xbox One S