Should I upgrade DAC, speaker cables, ICs, or PCs?

I agree with upgrading the source first in terms of biggest bang for your buck from the remaining upgrade areas you mention. I view speaker cables, ICs, and PCs as the last thing to upgrade once you have your main system dialed in as best as you can get it. Many people use cables as tone controls to correct something else upstream in the signal chain. I would try to get the best and most synergistic components first and then try to get the best cables you can afford that will do the least amount of degradation to the sound. So go for source first. Many options here: 1) upgrade to another 1 box CD, 2) upgrade to a 1 box CD/SACD or even unversal player (if you care about SACD, DVD-A and Blu-ray), and 3) keep the Rotel 1072 CDP as transport and get a DAC (many of the aforementioned are excellent but be sure to get something with excellent jitter reduction). Option 3 allows you the flexibility of also adding a computer as a source. My 2c worth.

If you're interested in a computer as a source then look at Spatial Computer. It'll trounce the other components I mentioned, and is currently what I am using. The website is all mumbo jumbo, but I worked in recording for a number of years and now in audio post for film so I can help you out if you don't understand the BS on the website!

The one component you might try is an Oppo 83SE for your digital. Or, a Sony 5400 from the place advertising here that sells them for $1050.
Either one would be a good upgrade from your Rotel CD.
I would stay away from the cables.. a road to Audiophile madness? The ONE thing you could do is find a cable well praised by mags and folks alike. i use Kinber as they have a LONG history if praise. i use Hero, and 8TC. I have used PBJ. (Hero seems to be the new better PBJ) 8TC has been a great choice for many years. (though beware used unterminated 8TC clear.white as many, many Chinese fakes for it.)But for me, i would go for Oppo 83SE or Sony 5400 as a basic, great well reviewed choice

Great feedback!

Actually, I'm surprised everybody went for the source as the first step. It's unusual to get an unanimous answer in this hobby. Maybe the question was too obvious, not to me anyway.

Sorry about the typo: the Rotel is a CD player indeed. Don't know why I typed preamp there...

While I haven't been able to try how cables impact the sound, I tend to believe they do. Unfortunately I live overseas in South America so borrowing from the Cable Co is not an option, and there aren't many hi-end cables around here to try, let alone borrowing for in-home audition. So I'm stuck with educated guessing. The best way 've found so far is digging threads here and contacting folks with systems as similar as possible to mine (albeit different tastes) and get their input as to what worked and why/how.

From that I was thinking using the Rotel as transport for the DAC3 (mentioned), or Benchmark (mentioned), or MHDT Havana, to name 3 that come to mind now. I like the idea of computer audio down the road, but as another source as opposed to replacing the CD transport.

For cables I am surprised to get the feedback of PCs first, but this is part of the learning I am after.
For speaker and ICs I had good comments about Kimber 8TC and another model up I can't recall now, Purist Audio, Transparent, or Nordost. I know of two people with B&W speakers who swear by Nordost Frey and Valkyrja speaker cable, but those are close to $1200 used and I have a hard time justifying that for my system.

What I'm taking away then is use $1500 for: a DAC and a digital IC for transport to DAC, and do the rest as funds come up. Example: a DAC3 is listed for $1295+shipping, leaving about $200 for the digital IC.
Later, when funds permit get PCs for the DAC and Rotel transport, and even later ICs and PCs for pre and amp, and finally the speaker cables.

Am I making sense?
Thank you for the very good feedback!

Never upgrade a cable when you can make a legitimate component upgrade.