I've drilled plenty of holes to make components fit and it's not a problem IF done right, if you are hitting copper, not bending leads over to the copper.
However you have not mentioned a critical parameter which is lead spacing. You don't need 4 pins (though if you move this around much, or even if you don't, you might want to put a couple blobs of adhesive on both sides of them to help fortify the mechanical connection - NOT hot glue, it must cure to a warm temperature stable state).
Anyway, in this type of application the values for uF and voltage may not be as critical as in some, but without voltage measurements I'll err on the conservative side and suggest to get at least 50V caps. Capacitance, it wouldn't hurt much to go up or down a step or two, but I'll put 8200uF into Digikey's search parameters and out pop these hits:
Capacitors – Aluminum Electrolytic Capacitors are in stock at DigiKey. Order Now! Capacitors ship same day
www.digikey.com
They don't need to be the "Audio" caps at all, though depending on the amp design, there may be some benefit from higher ripple current rating and lower ESR rating.
Even then, I'd be tempted to get the following because their 5,000 hr @105C temp rating, should indicate longer life, though in this application, many should provide decades of service unless it's scorching hot in this amp.
Order today, ships today. LGY1H822MELC35 – 8200 µF 50 V Aluminum Electrolytic Capacitors Radial, Can - Snap-In 5000 Hrs @ 105°C from Nichicon. Pricing and Availability on millions of electronic components from Digi-Key Electronics.
www.digikey.com
The above assumes you have 10mm lead spacing, if not then go through Digikey's search again and spec the lead spacing you need.
I'm curious why you had settled on your linked, 80V rated cap when you stated it only needs to be 50V?
There are dozens of other options too, but not knowing how much space and lead spacing and other factors, these should work.