Yes, at the very least you should open it to take a look, not because it is old but because the company who built those power supplies for Antec at the time (CWT) used some of the most unreliable capacitors ever (Fuhjyyu) during the plague era. So they're almost guaranteed to fail as soon as they get a little hot (if they haven't failed already).

A couple of years ago I got a NOS PP-300V, which is pretty much the AT equivalent of your PSU, and when I opened it to check (before even trying to turn it on) half of the caps were bulging and/or leaking. You can probably leave the two large bulk capacitors, as those are not known to fail often (and at least in my case they used a good quality Japanese brand for those).

EDIT: the power supply design is very good for the era, as the article suggest. The only problem is the choice of caps, so if you replace them with quality ones you should have a great period-correct PSU.

I have an old topower 420W PSU, the metal is all mirror finish, very heavy.
I still have not opened it yet but i do plan on opening it and replace all the caps (not the 2 main big ones)

Im wondering if i should buy replacement caps that are LOW ESR or even buy solid polymer capacitors instead of electrolytic ones.

No, don't go with polymers on an old power supply. First of all, you probably won't be able to easily find polymers with the capacitance you need for the output. Also it is said that the extremely low ESR of polymers can mess up the feedback loop and even if it works you may end up with more ripple than with the older capacitors.

Ideally you want to match the specs of the original as much as possible. If you don't have access to the datasheets of the original caps, a good rule of thumb is that the caps on the output rails usually need to be low ESR, but for those older units just go with entry level low ESR caps from quality brands, that will be closer to what was available at the time it was designed. For the smaller caps you can use anything as long as it's rated 105C and from a reputable brand.

Despite its age, it works and no capacitors have leaked. But it smelled old electronics when I opened the box.