An antiquated DAC or an affordable recent one?

An inexpensive digital to analog converter is next on the purchase list. Should I opt for something new, (such as a Musical Fidelity V-Dac or Cambridge Audio Dac-Magic) or retro (like a Theta Chroma 396, Ps Audio Superlink or Adcom 600)? It is now, sadly, only listening via Sennheiser Hd 580 and Creek OBH-11, with a cheap Cd player. Rock and pop are the musical tastes.
Since the technology for DAC's changes fairly quickly, I think you would do better getting something 3 years old or newer. I don't know what your budget is, but based on what you're describing above, you may like the Benchmark DAC1 with the built-in Headphone Amplifier. It's a great DAC and the headphone amp section should be a huge improvement over the Creek. One just sold for $600 here.

I would personally buy used when it comes to a DAC, people upgrade all the time, why should you take the hit on depreciation.

Let me make another recommendation for you; since you don't have speakers right now, consider a set of Audioengine A5 Powered Speakers, they're $350 and they sound fantastic in a bedroom or hooked up to your Computer (iTunes), ipod, or CD Player as your source.
I just recently started looking into DACs. Everyone and everything I've read tells me that newer is better. Technology is cheaper, what used to cost $1000 a few years ago is bettered by $300 today and so on. Take all that with a grain of salt IMO.

A local dealer had a Theta Cobalt 307 DAC (precursor to Chroma) that he took on a trade for a Naim HDX. I took it home and tried it out, not expecting much. My dealer knew nothing about it other than the previous owner used it with a mega-changer CDP and he was the only owner.

I connected to to my Rega Apollo, which IMO and a lot of other's opinions is the definitive $1k CDP. Compared to the Apollo's analog outs, its surprisingly better in most ways. Its more detailed, cleaner sounding, and soundstage and imaging are a good deal better. All the audiophile stuff. But it lacks that very last bit of grooving the Apollo has to my ears. Very, very little bit - not even 1% IMO. Everyone's idea of musicallity is different and very subjective.

I say this because a 10-15 year old DAC should not be able to compete with a current $1k giant killer CDP in any way, yet in all but one way it beats it. I've heard a few new DACs. The only one I'd take over mine is the Bryston BDA-1. Researching the BDA-1, I read that they said they were very surprised on how little the chip contributed to the final sound. They said power supply, output devices, and things like that made far more difference. Makes sense to me.

I think the main advantage of the newer DACs is their ability to reduce jitter. Transports have less effect on the music, I believe. Newer ones also usually have more inputs, USB, and some other features.

My experience told my not to believe the hype. Newer doesn't mean better, so long as the DAC was designed properly and they paid attention to everything and not just the chip.

Also, I'd drop Adcom from your list. Every Adcom source I've heard was sub-par. Their pre-amps and amps are decent, but their CDPs were awful to my ears. I haven't heard their DAC, but from their CDPs, I wouldn't give it a chance.
I've owned some older Audio Alchemy dacs, some decent CD players, and a CAL Alpha DAC which was one of my better hifi purchases some time ago. A while back I started out looking for a cheap DAC to connect my cable box and DVD player to in a 2.1 system used mostly for music. What I ended up with was a Channel Islands Audio VDA 2 DAC. What was going to be an auxilary digital source ended up being my main source. For $599 this dac is awesome. I don't know how digital can sound any better without spending three or four times as much. I had listened to the Benchmark dac several times and preferred the VDA 2's sound and simplicity. There are only two switches, a quality chipset, and discrete output. Nothing against the DAC 1 it's nice, but I wouldn't use it for anything other than a DAC so I thought I'd be paying for stuff I wouldn't use.
IMO you should go with a new UPsampling dac like the Dacmagic or the V-Dac.They will turn a cheap transport into a redbook player that will compete with the others out there below $2000.00 anyway.Read Stereophile two monbths back they did a review of the V-Dac and the Dacmagic. I have never heard anything that comes close to my Dacmagic and Musical concepts transport.No I have never heard any players over $3000.00 so I cannot say about them.
Here's my little bit. I have an older Micromega DAC 1 and installed the Burson Audio opamps. Totally changed the sound and very pleasantly surprised.
Sorry, was too quick to post. So, another option is to take an older DAC and mod it.