USB Interface as Sound Card??

If you are using it for recording etc. I'd advise against it.  You probably won't have a problem but the various sample rates/bit depths/formats you'll find on the internet, youtube etc. can drive some drivers bonkers (my TC Electronic being the case).  And I don't understand what the headphone output being shot has to do w/ a family listening, but I'll skip that.
 
If you must use the presonus you'll have to go to Windows<Sounds and choose the driver for the presonus to take over all the sound duties - if I remember rightly.  I'm on a windows 8 machine right now and have no idea how to do in in 8, but earlier OS's made it pretty painless.
 
Hope this helps.
 
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Bu
 

I don't have a problem with my RME unit. I installed the drivers and use the ASIO drivers for Sonar, and anything else is whatever drivers came with it for Windows. In Windows you either mark the output 1 & 2 for Speakers or in my case output 3 & 4 for headphones output. Since in Sonar I have recording timing master as analog 1&2 and playback timing master as 3& 4 I just keep it the same. However if you have ADAT and wish to use that then on the Drivers output in Sonar you have to mark all of them with the checkbox or with the Input for the ones you have to use.
In Windows 7 I mark the default in the mixer of Windows to the Analog 1&2 Input because that is what I would normally use (with ADAT marked in Sonar when needed and in the Windows OS mixer), and the output in Windows with the Headphone graphic I mentioned up above because I use the Analog 3 & 4 outputs which in Windows is that headphone graphic instead of the analog outputs 1 & 2 in which case in Windows that would be the graphic - speakers). I have changed sample rate (actually forgotten I had the unit on a different sample rate like 96kHz and have had no problems because places like utube or most places are using Flash on your computer from Adobe Acrobat.
http://get.adobe.com/flashplayer/
So since it is streaming from their servers unless you know that you need to change sample rate to the usual 44.1kHz
or perhaps 48kHz with Windows Media Player, you just hook up your USB interface (and make sure the in-build computer one in the BIOS is turned off so it does not interfere - if you see it no more in Device Manager then you have set the BIOS correctly if you have a built-in RealTek whatever sound card in your computer). (Might as well get rid of the drivers by deleting it out of Device Manager if it shows and also un-installing the drivers or Windows 7 keeps everything like a packrat.
 
I listen to music, record music and been using my RME Babyface for the last 3 years as the only sound card (actually it is an audio/interface) with no problems, watching movies whatever all goes through that USB audio/interface just as any sound went through your other sound card whatever in the computer.
 
And to me most streaming music websites will be using Flash or something that even warrants that changing sample rate (always the bit depth is usually 24 bit but even if it is 16 bit I do not have to change anything maybe because the drivers for my audio/interface are that good).
 
If unsure, ya, you can keep the sample rate at 44.1 kHz like a CD would be but I just found that out with mine and it did not make a difference. For movies I just use the normal 44.1kHz, but even then sometimes I have been on 48kHz for a movie, and Windows is suppose to have programming that transforms the signal into having the proper sample rate and bit depth (say even if that is necessary) so none of that has to be done anymore.
The only thing I can not do like what could be done with XP OS, is change the volume on the output in Windows 7 because unlike XP, Microsoft changed since Vista how they program that. Now some websites may change the volume and sometimes I read like it is putting out 67% instead of the usual 50% but it does not do anything. Perhaps in XP OS it would and I use to be able to change it there and run up to 100% or down or anything inbetween. But since Vista, it makes no difference anymore, and if I want to change the volume up or down I do it with the software of my RME Babyface unit and the TotalMixFX program included with the RME drivers or with my computer speakers I have a volume and bass and treble control to change things. Yes, some videos are way louder than others normal ones, so that has to be watched because of the loudness wars they think everyone wants to put up with or hear their sounds louder for some reason. So I watch that in TotalMixFX program from RME and if a video does that, I down the volume in that program. Usually I would not have to because a good digital unit would have enough headroom even running in the red on some videos to not sound bad, but since they are running my unit in the red, I down the volume in that TotalMixFX program that came with the audio/interface.
 
With a USB device it is better to look in Control Panel and make sure that the USB ports always have power on (not go into sleep mode) and that you have a good USB 2.0 port because some USB3.0 ports will not work correctly for a USB 2.0 connection. I have USB3.0 ports on my computer but I do not even use them as far as I know, and I just have my unit plugged into the USB front port on the computer, and you hook up the unit like any other soundcard with the speakers hooked up to your audio interface.
 
That's about it, and nothing strange about it, just like any other soundcard you have to tell Windows what output you are using (even though all the ADAT ports are there as well as well as the HDMI on my graphics card for hooking up video and sound to an HDTV or a computer monitor that has sound and video which can be hooked up that way. Otherwise with just speakers (self-powered amp in those) you just run the audio cord like a balanced cord or guitar cord type with an adaptor if needed (my stereo amp has phono RCA inputs in which case I use an adaptor from the 1/4" phone plug balanced or not (like a guitar cable or synth cable) and go in my stereo that way using the adaptor connection on the end of the cable. If you have XLR outputs like on my unit then you need a XLR cable to a say 1/4" balanced (guitar) type cable or if the speaker has XLR connections and my unit has XLR connections then it be like using a microphone cable out of my audio/interface into the speakers XLR connection in the back of the unit.
 

*most* of what you guys have said makes sense to me. My problem early on is simply that... my interface doesn't show up as an audio device. It's of course in device manager (under PreSonus USB 2.0 Audio Devices) but I get nothing for it in the "Sound" panel of Win7, etc... Before we continue, what's the fix for this issue?

I would right now say that you are just looking at it wrong. And in Sonar you ought to be able to tell if all drivers are present in the Options menu item Audio submenu item where you change what drivers you want to use to record with in Sonar. Of course ASIO drivers are the best for audio wave file recording to record with, but if I wanted to I could use the WDM/KS drivers (Windows OS drivers) also to record with and have latency or even MME drivers (which are really bad for latency) to record with in Sonar.
 

ah, I get it spacealf! I did indeed NOT have WDM drivers downloaded. I only installed drivers out-of-the-box, I didn't look for updates on their site. I suppose now would be time to read up on the wealth of knowledge you guys posted in terms of sampling rates and stuff. Thanks a bunch, guys! If I need any help, I'll know where to look

here is your drivers current version and manual in whatever language you like to read it in.
 
http://www.presonus.com/support/downloads/audiobox-usb
 
(drivers should have come with the unit, at least the older drivers version).