Integrate 2-channel or go all 5 channel

I'm at a crossroad and could use some advice. I'm looking to integrate a 2-channel into my HT environment. I have ~ $4K to spend and cannot decide whether to drop all of it on a modest 5.1 pre/pro and amp combo and retire the receiver, or integrate a 2-channel into the mix. Would I get significantly better sound from a 2-channel setup integrated into my existing environment? If I went 2-channel, I think I could do it for about half my budget. Today, I'm leaning towards the 2-channel. My preferred amp would be a McCormack DNA ??. I'm looking for recommendations for a pre-amp. The requirements are, HT passthrough, and a remote. I have 2-way monitors and want to keep my sub in the 2-channel mix. Does anyone make a 2.1 pre-amp? I also need some way to set the frequency cutoff between to mains and the sub.
Based on the need to use my sub, next week I'll probably be leaning towards all 5 channel gear, amp there probably would be a Bryston.
There are a couple questions buried in the above diatribe. I sure could use some guidance.

Existing equip:
Yamaha RXV-995 receiver
Vienna Acoustics Haydn mains
Denon DVD-1600 DVD/CD/DVD-A player
M&K MX-150 sub.

My musical tastes are mainly rock & roll, if you think Pearl Jam, that should give you a good idea. and techno(house mainly).

Thanks in advance