No the RX-4105 does not have a sub out. Your powered sub must have speaker in and out connections. You would run the speaker wire from the receiver to the sub and then on to the speakers. You then use the crossover dial and the sub volume on the sub.
You would hook up the speakers as normal, speaker wire from the receiver to the speakers. Run a single RCA cable from the sub out on the receiver to the line in on the sub. If you have more than one line in on the sub then it depends on the particular sub (we would need the model number of your sub to give you specific hook up advice).
In this case you use the sub crossover setting in the receiver's menu. Depending on your speakers you would most likely set the crossover to 80Hz and set the speakers to "small" (regardless of their actual enclosure size). This then would send all frequencies above 80 Hz to your speakers and all below 80 Hz to the sub (this is the THX standard and is usually best for most speakers except for very small bookshelf speakers). The receiver would also control the sub volume.
On the sub you would set the crossover dial to its far clockwise setting, the highest setting possible. If the sub has a "bypass" setting you would use this instead. Set the sub volume control to about 10-11 o'clock and usually leave it there.
What you are in fact doing in this instance is controlling the sub crossover and volume from the receiver and bypassing these controls on the sub.
To give you the best advice we would need the model numbers of your speakers, the sub and your new receiver.
I think you might find some stereo receivers that have a sub out but not the bass managment settings like I mentioned above. I believe Outlaw Audio has a great stereo reciever that does but might be above your budget. Otherwise you should look at a AVR 5.1 - 7.1 receiver and use only the two main amps for stereo playback (make sure the sub out is active in this mode). Later you might find that you will want to use 5 speakers plus the sub for stereo enhancement and multichannel sound. I find it superior. Many here disagree. However it is in fact superior IMO if you set it up correctly. That requires that you have all 5 speakers voice/timbre matched from the same brand and model series and also that you set up the speaker volumes to within a 0.5 decibel tolerence of each other which takes an inexpensive Radio Shack sound level meter. More on this at a later time if you ever are interesested.
The outlaw specs say that the 2150 is: "•The only stereo receiver with a subwoofer output that includes selectable, analog bass management "
If this is acurate you can find decent AVR receivers starting at about $250 list and up (many are discounted online). Otherwise you can set it up as mentioned in the above post using your RX-4105 which should be fine except for running lots of speaker wire.
That is to say a NIB stereo receiver that sells for $100, give or take. I[m responsible fot placing these into the systems of several friends who simpy wanted a very good sounding stereo system while not spending a lot of money. All are more than satisfied. So am I
The fact that only has two channels makes it a better performer (in stereo) than many entry-level muti-channel HT receivers.
A decent sub running via speaker-level in/outputs can sound very, very nice indeed.
Think about what you really want, what performance you expect, and how much you're prepared to spend. That Outlaw stereo is very, very nice but it's not in the same league.
Most subs can also be hooked up to the speaker terminals of the receiver if there is no sub out.
Pass Labs X250 amp, Pass X-1 Preamp
Magnepan QR1.6 speakers
Van Alstine Ultra Hybrid Tube Preamp and Ultra Hybrid Tube DAC
Martin Logan Original Dynamo Sub
Vintage Luxman T-110 tuner
Magnepan MMG's, Grant Fidelity DAC-11, Class D CDA254 amp
Monitor Audio S1 speakers, PSB B6 speakers
Vintage Technic's Integrated amp
Music Hall 25.2 CDP
Adcom GFR 700 AVR
Cables- Silnote, BJC
Velodyne CHT 8 sub