The HTS 7.1 was a $8000 processor, and I think it was an extremely good processor. I had it for a long time. It makes a good 2-channel analog preamp, though I would say that it’s slightly soft for a 2-channel preamp because of its analog input stage. It can sound very good when used as a digital DAC/processor, but it is getting very old at this point.
The McIntosh MX150 aren’t that old. They are only 2 generations old and MX150 does support HDMI and bluray formats. Though, it is not new enough to support 4K (it’s only HDMI 1.3). I suggested it because you liked your 2-channel McIntosh setup.
In reference to your Denon, it is a receiver, which means a good portion of the unit cost has to go into the amplifier section. It may sound okay, but you’ll get much better sound quality with a dedicated processor. I recommended the Marantz because it does have an excellent design for a processor at that level. Good power supply (2 x 10,000uf capacitors) and discrete balanced output stages. Sonic signature is a little on the warm side, so it will not be as fast on the attack as the Krell stuff (or other processors such as Anthem or Arcam). I wouldn’t go for a KRC3 since you already have such an excellent 2 channel system. I think the Marantz will do a good 2-channel representation as well as provide for a good theater experience. The KRC-3 is on the warm side and others have had better experience with something newer like the Parasound P7.
Trying to make an awesome sounding 2-channel plus home theater system is going to cost a whole lot of money. The best you can you can do with that budget is something decent. It's not going to compete with your McIntosh 2-channel system, but it should sound pretty good anyways.