Hey Jam

I have heard about Newform Research and I did check out the website on the R645. I must say this is a very impressive speaker you got. For music you don't really need a sub on with these speakers but for home theatre a proper sub IS needed like your SVS.

Newform states this about the speakers......

"For home theater systems the majority of users will want a very good subwoofer with the 645v3 since it can operate solidly into the low 30s and can be crossed over well below 45Hz. Owners frequently run the 645s full range with the sub as augmentation rather than replacement at low frequencies."

You see Jam....the R645s operate solidly into the LOW 30s. Since your SVS 16-46PC goes down to 16hz then a crossover at 40hz will be needed on your system. I know about the power of SVS as I own a new version of the PB13 Ultra.

If your Oppo 83 can only do 80hz I take it you do not own a pre/pro with bass management that hits down at 40hz. You may need to replace you Oppo for the 93 or 95.

Also note that even in the low 30hz region your SVS will totally out perform your speakers so a 40hz crossover is the best. You may want to experiment with 50hz and test it on a movie you are familiar with. In closing you got to get down to 40hz somehow either by a new player or by a pre/pro for bass management. Then meter out the power to 75db on the speaker system and 78db on the sub and Bob's your uncle.