The R32 was a serious contender when i was selling the Zed and again when i was selling the S2000. i really like them, very much a stealth car, not a lot to give them away apart from the twin exhaust, the badge and the wheels. i loved the Mk4 recaro seats, looked stunning. tip is to go for the part leather ones, as the full leather ones tended to stretch in the middle section and look saggy.
difficult to find good quality low mile ones or un molested ones but they are the best to go for, preferably the blue, or the black look best. engines are pretty solid, tended to have a few minor issues like needing new coil packs etc, but nothing major, and no different to run really compared to the zed.
power and performance is not disimiliar to the zed, both are very smooth, both are deceptive of how fast your actually going. would say the R32 has the nicer interior over the Zed, really nice blue dash and dials.
really good extras to get and worth a look on you tube are things like the milltek unresonated exhaust, makes the V6 come alive, and really is a stunning sound, would possibly say better than the zed.
driving wise; the R32 is a good drive, the haldex 4wd system is nice, can;t always tell when it does or does not kick in , but the car does stick well in the corners. far easier to chuch around on country roads as there is a lot more grip. but would possibly say the Zed is a little more rewarding to drive if comparing stock against stock car. the haldex works as a front wheel drive car but kicks in the rears with power if they start to slip. you can get haldex controllers that alllow you to shift the bias of % to the rear over the fronts i think.
if you like the R32 the other option is the early audi S3's same car, but instead of a V6 its a turbo unit and you can easily tune the nuts off them for silly power.
R32 wise, i liked thedrive of the mk5 but loved the seats in the Mk4, the mk5 was more refined, and i loved the DSG box in it. both good cars and you can't really loose out as they hold their price well.
as a replacement for the Zed, its got to be a personal decision, i think its a good one, but you'll need to test drive it yourself to decide.