PSU Upgrades for Cambridge Audio DacMagic...

There are many happy users of Rock-Grotto units (little pinkie) so it will do no harm to your DacMagic. The Russ Andrews unit does'nt look bad either: both are just a 'better' spec transformer than the original.
Remember your DacMagic uses AC current, so there is not much to be improved besides the transformer itself. Other units (say as V-DAC) use DC power, and there is much more room for improvement to be had from their crappy walwart PSUs: not just a better and eventually bigger transformer, but also better and cleaner rectificaction, filtering and regulation. Those three key points are alreday quite well done inside your unit btw.
But as said, a nicer/bigger transformer will do no harm. Let us know if it does some good things

Would anyone who knows more about hi fi than I do be able to tell me whether these upgrades to the dacmagic are reasonable for £180?

Cambridge Audio DacMagic DAC Level-2 Audio Upgrade on eBay, also, CD Players, Home Audio Hi Fi, Consumer Electronics (end time 24-Apr-09 12:00:12 BST)

I don't know for sure, but giving the price of the CA DAC magic, it's likely you would have been better buying a different DAC rather then the CA Dac magic and those mods. Though I may be wrong as I strongly believe in the percieved difference (what you hear) rather then what technically should make it 'better'.

There is probably not much to gain. You see, the complete 'psu' you're thinking of is inside the DM. You're only upgrading the transformer. That for 100€.. Meh.

Gotta agree with apatN on this. It doesnt look like the Dacmagic can benefit much from a walwart upgrade. I dont think much can be done without some serious modding.

Doesn't make sense to dump more money in "upgrades" for this thing than it costs. Would be a better value to simply spend the cost of the DAC + upgrades on another unit.

Actually these mods make a lot of sense, many wall warts are non linear power supplies and don't do a very good job at giving you stable current and/or voltage. The reason it is possibly worth moding the cambridge is because The DSPs inside aren't really in other USB DACs. Anagram DSPs are known for their re-clocking. If you are going that route, that is pretty much the best out there. While Re-clocking is controversial it makes it so the clock data from the computer is inconsequential since Computer Audio has clocking issues and are non synchronous this is the only solution out there other than what Wavelength and Ayre are doing with their USB DACs, and At this price point this is probably the best USB DAC out there. It also has UP sampling to 192kHz and has 32 Bit floating point Math, plus it has Balanced output and multiple Digital I/O. I kind of wish Cambridge had made this an IEC unit with Transformer, but alas they didn't. A linear power supply with good filtering caps and more stable current should help this unit sound very good. Keep in mind many DACs actually use Aspects of the AC wave form in their clocking So getting stable power is important for the analog section and digital section. Another Mod might be to change out the Caps, OP-Amps, and resistors to something more robust like OPA 627, Auricap, and Vishay Dale. All of these MODs might make this thing a Total of 1000$ at the most and even at that price it is a good deal. Keep in mind these are the Same output devices in their 1000$ and 1700$ CD players.