Alpine Type-R 6.5 and 6x9 with F600 Amp Underperforming - Replace 6x9 with 6.5" sub?

[BaumermaN]

I installed alpine SPR-17C and SPR-69C, both Type-R with 100rms each, I am using the Alpine CDE-102 HU, and Alpine F600 amp.

6x9"
» power range: 2-100 watts RMS (300 watts peak power)
» frequency response: 60-27,000 Hz
» sensitivity: 89 dB

6.5"
» power range: 2-100 watts RMS (300 watts peak power)
» frequency response: 65-27,000 Hz
» sensitivity: 87 dB

Amp
» 4-channel car amplifier
» 100 watts RMS x 4 at 4 ohms
» variable high-pass/low-pass filters (50-400 Hz, 12 dB/octave)
» selectable bass boost (12 dB at 50 Hz)

I have been very disappointed with the bass coming from the 6x9s. I have the 6.5s sounding great with HP filter on from the amp. I had the 6x9s set without any filter on them for a while and disappointingly I was getting a lot of distortion trying to turn the bass up at all, some sounds would sound great from it and others would simply be distorted. I played with the gains on it a lot and never really got anywhere. Today I changed the 6x9s to HP filter today and was able to adjust it so I can give them more power without distorting but obviously I am missing a lot of the deep bass i am looking for.

Anyone have a setup similar sounding good?
I cant put subs in my car, I had them in my old car, but need the trunk space in here. Am I better off selling these and grabbing some 6.5" subs? Any recommendations?