Thank you all for your replies. In the mean time I stumbled upon an offer I couldn't refuse; a Dell R200 (see sig) for very little money, and 1 HP V1910-48G for even less money. I have been fighting with this machine for a couple of days (not necessarily the machine's fault, as I fight with every machine I come across ;D) and I have to say by now it is working very well.
Now I would love to get my two pfSense machines in full automatic CARP, but it appears that won't be easy. Well, at least I now have a backup pfSense and a backup switch.
Ah, before I forget, for future noobs like me: I bought this machine as it was on sale (refurbished) in the pfSense store on this very forum. If the great men (and women?) who create pfSense sell a Dell R200 there should be no doubt that it will work, so hence my purchase (not from pfSense, as it appeared shipping these machines from the USA to Amsterdam was triple the cost of the appliances itself thanks to the mentally retarded 'Fedex'-and alikes of this world. It would amount to 500-600 USD just to put these in the belly of the big Boeing).
Thank you again for your suggestions ;D