So, I just took home a mint Boston VR500 sub for $20. Want to pair it with my Boston T830s lcrossed over at 40hz for music only. Now, I use a Sony TA700 ES integrated. Hook up options are limited---speaker level and out to mains or Towers A and Sub B. Sony does have an Adaptor switch, but I'm but I'm not sure that's a true pre-out. Is it!?! I like to run the amp direct---sounds great. Opinions welcomed...thx!