Yes, an ARC LS16mkII, 25mkII or REF2mkII would help dramatically in the drive/dynamics/life department. I'm an ARC and ProAc dealer, so I have some experience with your gear. Everytime I have tried eliminating the preamp, the result is somewhat lifeless yet transparent sound. The newest ARC preamps are so transparent that you won't get any downside to inserting them in the system. They will help control the bass better as well.
As for the boomy bass, this is a tendency of the Response 3.8 speaker. They need to be far away from walls to have a chance. Also, you need speaker wire that is fast and tight in the bass. This means no stranded wire and preferably very carefully chosen solid core wire.
The only other recommendation I can make from experience is to try a Vandersteen 2Wq subwoofer (or preferably a pair). They improve the sound of the system dramatically by removing a portion of the bass burden from the ProAcs, while also helping the amplifiers as well.
Good Luck
As for the boomy bass, this is a tendency of the Response 3.8 speaker. They need to be far away from walls to have a chance. Also, you need speaker wire that is fast and tight in the bass. This means no stranded wire and preferably very carefully chosen solid core wire.
The only other recommendation I can make from experience is to try a Vandersteen 2Wq subwoofer (or preferably a pair). They improve the sound of the system dramatically by removing a portion of the bass burden from the ProAcs, while also helping the amplifiers as well.
Good Luck