Hi :-)
I'm using an X-Surf card as I type that message :-) works like a charm :-D since more than two year now in my A4000 (see my profile for the configuration).
I have an x-Surf II too in an A4000T (the REAL one ;-), and it works the same :-D no problems at all with Miami Deluxe (registered).
I have an Ariadne I card in an A3000, no problems too, but that card is quite rare today ;-) BTW, the extra parallel port on it is usefull :-)
I have an Ariadne II too in an A2500, works great, but rare too now :-)
Go for the X-Surf II, it's a good card, in fact it's TWO good cards as it is a Zorro bus adaptator card with A1200 compatibles clockports and 26 pins extention port, coupled to a Kingston PeeCee ethernet card ;-) Very good built and reliable (at least here ;-)