Which computer for digitizing and streaming?

Hi, I'm getting started on pc audio, and still not sure what software is best for a retiree and an idiot on computing, but one thing for sure is the standard windows media has worked for me so far. I have however noticed differences in sound from different computers. I have 3 different laptops that I use with my main gig and they all sounded different.
I believe what "rgs92" is right about getting a dedicated computer for the best result.

I'd go with a Mac Mini. Matter of fact, I did. 

You could go with a Windows-based platform, but I think you'd spend a lot of time trying to squeeze performance out of it, and to figure out what went wrong. A dedicated Mac is just much easier and less prone to issues, IME.

Get a Mac Mini, set it up with an old monitor, keyboard, and mouse. Then put it on your rack to run headless, controlling from an iOS device such as your phone or iPad using Apple Remote, or from any other Mac in the house via Share Screen. (You'll need WiFi, of course.)  Lots of info on the internet about how to do this, and optimization is easy.

For the Mac Mini, get one with an internal SSD drive to reduce mechanical noise. Use the SSD only for critical software and OS X. Then get an external HDD hooked up via Firewire 800 or better, or if you're feeling more ambitious, an NAS. Benjamin at Mojo Audio does a good job of using an AV drive in an OWC case with modifications.

After you've established your library -- in iTunes, most likely -- you'll want to use iTunes only for library management, as it's less than optimal for sound. I use PureMusic and love it; Channel D also has Pure Vinyl which includes PureMusic but is more geared toward vinyl reproduction. You could also use Amarra or Audirvana, but the thing to remember is that you want software to pull the files out of iTunes and handle them properly.  BitPerfect is a clean and inexpensive option as well.

All in all, this is all about setting up a dedicated system to do one or two things well, and then tuning it to just do the basics.  It's easy; it's a one-time thing, and the results are fantastic when done correctly. And you won't have to get up and down for each album side!

PM if you need more info.

For software on a PC or Mac, you should look at Vinyl Studio. It takes a little getting used to, but the tutorials are quite good. It allows you to record, split into tracks (including looking up album information and track timings), cleanup (hum and hiss removal, click removal, repair of bad flaws), normalization and outputting to various formats. The trial version is free and the cost is only $29 - a real steal. As I said, it takes a little getting used to, as do all programs, but the results can be outstanding. I would definitely give it a try. I am up to about 200 albums using it. I can easily do 5 or more albums in a day with VS, assuming the records are relatively clean.

If you are getting significantly different results with 3 different computers, you need to look at the process you are using and what else is running on the computer. The output of the PC Audio is a digital bitstream which should be handled very well by most computers. The output of the PC should be to an asynchronous DAC. What DAC are you using? And what protocol are you using - WASAPI, Asio, DIrect Sound? For player software, JRIver Media Center is a good option. Before buying a dedicated system, I would try to figure out why you are hearing such different sounds on 3 systems. A well set up PC should not have that problem. There can be differences, but they should not be as dramatic as you seem to indicate.

Or...a Sony HAP for a simple one box wifi app solution and be up and rolling immediately.