TC Helicon makes great stuff. But 99% of people would just use a mixer aux send or insert to a normal delay unit if echo is what's desired. Depends on your setup. A vocal FX specific unit usually has harmony and pitch correct that needs to talk directly to the mic for processing. Other, more common effects can just be patched in with less headache. Again, depending on your setup.
I have a Behringer Minifex, that unit only takes jack input, so if you need XLR in, you need to put something in front of it like the Behringer MIC100 (around 50 euro's), or a small mixer that has XLR in (which is what I'm doing, because I had it lying around ). The unit itself is about 70 euro's, if you buy it new (I got it for 15 second hand). If you then need XLR to go to the mixing desk, you would also need a passive DI (starting at around 10 euro's)