My colour RU990 (TSU7500) has a Philips adapter that says
Input 240~50hz 60mA
Output 12v===400mA
And although my remote is an RU990 the docking station that came with it is a DS7500 so I assume all the docking stations are US/EURO and it is just the adaptor that plugs in that is different.
My Marantz RC5400 (same as the TSU3000) has exactly the same adaptor.
Take a look at your Pronto power supply on your old adaptor and see if that is the same.
There are loads of threads on remotecentral.com that say the only difference is the adaptor and if your old one fits you don't have the expense of getting one.
One thing I should add is the built in database of codes is very US/EURO biased, but 99% of people don't rely on that and rather download the codes from remotecentral or learn their own.
Also if you plan to use RF they are NOT interchangeable! So you will need to buy the matching RF extender if you plan to go that far.
Lastly, if you use X10 here in the UK the EURO Pronto can control that out of the box, if you use the US pronto you need an IR to Euro RF converter.
So in essence, although a US Pronto may seem a cheap alternative, as long as you plan only to use IR it is OK.
If you are more adventurous, by the time you have bought a power adaptor, RF extender and the IR to RF converter, you may be in the realms of the UK price in any event.
The USB to Serial adapter thing is a different ball game and I think some have missed how it works. You STILL NEED you old cable (or replacement) the USB to serial discussion is regarding new PCs/Laptops that have no serial port to plug the cable (the one you lost) into, so you get a USB to serial and plug that into the computer and then plug the pronto cable into that.
That must be the best excuse ever to upgrade as you need to buy two cables to do anything
A bit long winded but hope it assists
Stoobie