I have a purple tang, naso, and male blue throat trigger in a 90 gallon and they do all fine. The trigger doesn't touch my cleaner shrimp or starfish or even my baby ruby red scooter dragonet. I personally recommend you get a naso tang. Blonde may be a little more aggressive then the regular ones but they have an amazing personality. If you want to have a desjardini they tend to get aggressive as they get older. The regular sailfin is your better bet. I've had both and there is a big difference. I'd add your purple tang and the zebrasoma species last unless you plan to add all the tangs at once. I've had a yellow tang, sailfin, blonde naso, naso, purple, regal, desjardini, powder blue, and a yellow eye cole. And the easiest to care for would be naso and sailfin. Most difficult any of the powder blue or powder brown and the acantharus species. Having tangs is beautiful but some just don't get along and can't behave lol. And 5 tangs should be fine in a 125 gallon as long as you have good filtration. A good skimmer and a phosphate reactor especially since your going to have corals and with all the waste that is produced by the tangs those phosphates will shoot up.
good luck. Post pics when you have it all set up.
