Hmm... I think you're still good to go with the 3600. It's a good receiver and still plenty current.
The folks on Reddit might have a point. The first time I heard bass coming from a legit, clean powerful sub I was floored. I didn't know that bass could have such an impact on overall sound quality. It's always, always underestimated and back burnered by guys who haven't experienced it. Myself included. Now I know better, lol.
I think a pair of
Hsu VTF-2 MK5s would get you there. A pair of
VTF-3 MK5s (price is for 2 of them) even moreso. I am trying to take your budget under consideration tho, lol. Or
start with 1 VTF-3 MK5 and plan on a 2nd down the road after you replace your speakers. A more budget friendly option would be a pair of
RSL Speedwoofers. They're smaller, but pack a punch and come in just under Audioholics' large room rating.
I'm not familiar with your speakers but CV are competent manufacturers. They're not at the top of the heap, but you could do worse for sure. That sub tho... I would plan on spending close to 2k for your front stage and I'd get some bookshelf speakers in your shoes. Good sized ones. My logic here is that you can buy a little higher quality in a bookshelf where you would usually be looking at a lower tier tower for the same money. The money saved on materials, drivers and cabinetry in a tower can go into higher quality parts and electronics in a bookshelf. That's where a good pair of subs come in. With good subs to pick up the lower frequencies you won't miss towers, and I'd want subs with towers anyway.
SVS, Canton, Ascend, Kef, RSL, RBH, Monoprice- all great places to start searching for speakers. Accessories4less has been running some great deals for Canton. Oh, also the JBL 5** series pop up on sale all the time too. Great speakers also.