Are you saying you want a stereo system, possibly with a subwoofer?
That' s a little different than what's commonly called a "2.1" system, which implies a computer speaker with built in amplification.
It looks like you're headed in the right diredtion, though, sticking to two channel receivers. The key here is choosing your subwoofer carefully.
Some receivers have a "subwoofer out" on them. I've heard the H/K units do, which is good. But, even if the receiver you choose doesn't have this, tain't no big thang if you choose your subwoofer carefully.
Most subwoofers offer two ways to feed them. One has two speaker inputs, which allows it to be connected to the speaker outs of your receiver. this allows it to be used with virtually any receiver.
The other method uses either one or two RCA jacks so it can accept a "line level" signal from either a subwoofer out, like the H/K has, or a two channel preamp output. These generally offer more flexibility in making adjustments beeded to mate the sub with your mains.
Some, not all, receivers have "preamp outs" and you would feed both channels (R/L) to both line level inputs (R/l) on the subwoofer. If , like the H/K does, you DO have only a "sub out" on your revceiver, you can feed it into either channel or, for an additionnal $4.00 or so, you can get a "Y" connector and connect it to both channels. Many subs also offer another pair of RCA jacks that allow you to return tos siline level signal (sans deep bass) back to the receiver so that it's power amp doesn't have to handle the deep bass. This can lower the power demands on it and clean up the signal.
Some subwoofers have only one line level input. This can be troublesome if you're not careful. This will work fine if the receiver has a "sub out" like the H/K. This is what it was made for. But, if your receiver has only a pair of preamp outs (R/L), you can't use this configuration. You simply cannot combine the left and right preamp outputs into one input without a separate piece of gear. IOW, try to avoid these unless you know fer sure you can use it.
This leaves the lowest common denominator, the speaker level connections. If your chosen receiver han neither of the line level outs, this is your only route. Their use is self explanitory. Most subs offer speaker outputs as well so you can connect your main speakers to subwoofer, the sub will extract the bass and send the rest of the signal out to your main speakers. This relieves the mains from trying to reproduce the deep bass and generally cleans up the sound. The downside to this is that the subwoofers hard coded crossover points may not be optimum for your system but many people are happy as a clam at high tide with this setup. I'd give it a try before simply writing it off. It helps more than it hurts.
If your mains can handle a full range signal with having a nervous breakdown on deep bass, you can simply run it "in parallel" with your mains. IOW, the sub signal is a one way trip. The rest of the system still deal with the deep bass like it always has. In the case of speaker level inputs, simply connect it in parallel to your main speakers. I'd recommend connecting it to the same outputs as your speakers. Likewise, if you use the preamp outs, simply connect them to the subs inputs.
Ignore any outputs from the sub. In both cases, the signal, in it's original form, will still be going through the system as if there is no sub attached, with all the deep bass demands it always had. The sub will be acting independently.
Pwersonally, If you look at my system, when I had my sub in my two channel systsm, ran my sub from my preamp outs in parallel with the rest of the system. I was lucky in that my speakers were polite enough to simply any deep bass it couldn't handle.
I know I didn't offer any specific recommendations but I've always believed that a little theory on what's going on might help guide your future decisions.
good luck.
