amp with gain volume control

Hi, I want to bi-amp without bypassing the crossover in my speakers. Any suggestions? I just purchased a Parasound Halo A-23 for the bottom end. With the gain turned up completely it seems as though the bass is weaker than using my single amp. The amp that I am using is the Coincident Technology Frankenstein II. I just need an amp for the bottom end and I do not want to break the bank.
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I am using both outputs on preamp, one pair to the Frank the other to the Halo. The amps are just wired directly to the speakers. The Frank is to the upper posts, the Halo to the lower posts. Preamp is VTL 6.5 II. Speakers are Coincident Technology Total Reference.
All I can add is "Dragons" could run the whole show or just the bottom. I've heard them biamped with the franks and on there own with amazing results.

Disclosure: Happy Frankenstein owner!
Hi Montejay,

Thanks for the reply. I am very aware of the Dragons, but I do not want to break the bank. I want to keep it economical.

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Hi Zhzoller,
Would you consider the 'Dragons' on there own and not bi-amp? I've heard them with the pures which are very simular to your speakers, and the sound was nothing short of incredible.
I however,wouldn't consider selling my 'Franks' at this point in time.