someone help me please i am a newb

I am new to high(er)-end stereo, i was recently given a stereo system that I would like to start adding to. I have a Mcintosh C33 preamp into B&K ST140 stereo amp and dual 1218 turntable and i want to either 1)get a DAC to play my digital music catalogue stored on my dell inspiron 530 or
2)screw it and upgrade to a better turntable

I have a budget of ~$500-$750

that said, i would like to understand computer to DAC playback/, should i be concerned about the quality of my computer/usb output?...or does the DAC pretty much negate that?...and maybe some of you could suggest other things i need to think about, thanks
You will notice a benefit to upgrading your turntable when you do it, but I suggest getting a DAC right now because you don't seem to have anything except your Dell's audio out jack for playing digital music.

So I say keep the turntable upgrade in mind and start researching it, but spend now on a DAC and cables. Personally I would suggest the SimAudio Moon 100D DAC. It has a USB input which you can use for now. You will have enough cash left over to buy a good USB cable, like the cryo-treated silver one from Audiogoner Acreyes -- look him up.

Later, to upgrade your digital sound, you will want a USB-to-S/PDIF converter (one like the Valab Tera-Link X which sells on eBay for $60), plus a 1.5 meter coaxial interconnect cable.

That's what I would do, and there will be others who have their own favorite approaches to your needs and budget.
MY thoughts/opinions/experience... (you may get some polar opposite responses )....

The quality of your output on your pc...optical (if you have one)/usb, etc is kind of irrelevant...especially if you grab a usb to to s/pdif converter to tighten up timing... (even without this you can get amazing performance with a decent dac and lossless bit format).

This will spark debate--But IN MY EXPERIENCE, I've noticed Zero difference in performance of Digital cables (cheap vs. expensive) fact I have a/b 'd between my optical and coax dac outputs with very little sound difference...

For the kind of money your talking, I'm a huge fan of the PS Audio Dlink 3, it is a great performer...if you like warmth, body, etc (i.e. it's musical).... If you are a detail freak...there are better choices.

Don't let anyone tell you you can get hi-fi from a computer... I've got my "highest fi" using a computer and a great DAC. I will never go back to a CDP

Sorry...of course I meant---Don't let anyone tell you that you CAN'T get hi-fi from a computer.

anyway good luck...feel free to email me with questions about a pc/dac glad to share my experiences.
You haven't mentioned if your digital files are stored in a lossless format or the more common lossy MP3 format. If they are MP3s, the first thing to do (if you own the original discs) is to re-rip using something like JR River jukebox or Media Monkey in a lossless format like FLAC. Then I would recommend the HRT II+ USB DAC which costs $350 new and is powered off the USB bus so you can easily take it. I'd add a pair of decent RCA interconnects that you can buy used here for $100 and you would be good to go. The USB cable, to my ears, is not that important. If have some $ left over you might want to upgrade the interconnect btwn the pre and the power amp if its a basic freebie type.
The Peachtrees are the best for the money with USB inputs. Make sure your files are lossless or better as Swampwalker stated. I have a Musiland MD-10 which is great for the money.
Here are a few questions that should help responders more accurately provide advise. How old are you? How much are you willing to spend on your audio system over the next five years/10 years? What percent of the time do you sit and listen to your system as a primary source of entertainment and what percent as background while doing other things? How many LP's do you own?
-36years old
-I have 4 kids under 6 right now and working on paying off a mortgage in 5 years, that said, i think i could reasonably say~$5000 into my system seems reasonable
-i have no cable, no internet at home so when i do look for entertainment it is music or dvds. I would say 95% of h time i listen to music it is sitting in front of speakers with full attention on music, 5% background for reading/cleaning/playing with kids
-I honestly don't know how many LPs I have, i just started vinyl last winter...if i had to guess I would say ~50 that I listen to (then there is the crapload of "sing along with mitch" and big band records i picked up from my grandfather when he passed).
If you were truely a newbie, you would not even be asking or thinking about things like this. sounds as if you have been at least reading the high-end stuff for a while.
Rok2id, did you just call the man a liar?
no, just pointed out that the question / enquiry has 'audiophile' and 'high-end' written all over it.
the only newbie I have encountered on this forum is ME.
lol Rok...sorry, i am a newb to owning and buying high-end...i am just now cramming in some reading since i want a DAC...and boy am i in for some reading

I apologize for my outbrust. Believe it or not, I sometimes engage mouth / keyboard before brain. Welcome to audio. It's wonderful and affordable. Happy Listening.
if you decide to go the dac route, i recommend a used minimax, available on audiogon for about $600 ish.

regarding turntables, arms and cartiridges in your price range, a rega, with rega arm is a good choice, but then what cartridge ?? depends upon taste.

i suspect i will get some bricks thrown at me for this, because grados may produce a hum, i would consider a cheap grado.