DIY 12V PSU for a noob!

What is the intended application?  If it's for the 6410N, I wouldn't bother :p

Welcome to the wonderful world of DIY! And yeah, the laptop PSU is most likely a switch mode one. Probably too noisy and not recommended for audio.

If the included wallwart has two wires in the cable, and terminates with a normal looking DC barrel plug, then it's a single supply. If there are four pins in the plug, then it's dual.

I am not too familiar with the PSUs you listed. But I agree with FallenAngel that the Placid might be an overkill for the Kramer DAC. Maybe try a sigma25 (σ25) with a big heatsink. Relatively simple to put together for a first project and doesn't cost a lot. And definitely performs much better than a wallwart.

As with any PSU, make sure you know what your are doing when dealing with wall AC power.

Your 12V transformer should work fine with the secondaries wired in parallel. Even if it has a high max current output, it will only supply as much as is needed by the DAC.

I forgot to mention in my earlier post that the sigma25 is from AMB.

I would. Though not because one is superior to the other.

The Placid is a shunt regulator. I'm not too familiar with those, except that they are better suited for low current applications. And your stock wallwart has a 1.25A rating, which isn't terribly low. Also, you'll need to know in some good detail what levels of current the DAC will draw. I.e. will it fluctuate a lot, or mostly draw x mA, or whatever. And then configure the shunt regulator accordingly. With the Twisted Pear DACs, they know exactly what the power requirements of their DACs are, so no problem using the Placid there. I dunno, maybe your Kramer came with sufficient documentation to figure out what you need.

(These are just things I have read about shunt regulators, and have not attempted this myself.)

The AMB sigma25 is a simpler design based around a 7812 IC. It's good for up to 1.5A, and as long as you use a large enough heat sink you won't have to worry about much else. So I figure this would be better in that respect, especially since this is your first DIY project. It's similar to the power regulation section on your LC amp (from your sig). 

Oh, 150mA. That's not much at all then. No need for a big heat sink in that case. You might even get away with no heat sink at all, but I'd use something like the one pictured anyway to be on the safe side. But hypothetically if you were to use a big heatsink, you would mount the heatsink onto the board first, and then solder the LM7812 to fit vertically instead of bending 90 degrees.

The sigma25 in the picture is a bit non-standard, just in case you didn't already know. You will need to populate the D1 position for it to work with a transformer. It's just jumpered in the pic.

It's "better" in terms of cost and simplicity. And maybe with noise levels already below the threshold of the Kramer.

If you're up to it and want something with even better specs, then go for the Placid. I guess 150mA should be no problem. There's also the AMB sigma11. Tangent's YJPS is another top tier supply too, if you can find someone who still has a board to spare.

I'm just a relatively new DIYer with no engineering background. So maybe someone more experienced can chime in with a more in depth comparison.

First define "best". Then it will be easier to get an answer.

As for whether there will be any audible difference, that's beyond my ability or experience. I haven't tried the Kramer 6410N before. I'm basing my opinion off someone's comment in your Kramer thread (yes, I'm following that one; seems like an awesome deal at that price) about the DAC's specs being "below CD quality".

Now on the other hand, if the poor specs are a direct result of the stock PSU, then using a super high end PSU should help a lot. But that's a big "if" that I don't know the answer to.

In any case, the sigma25 is a nice "DIY 12V PSU for a noob" project.