Hi Paul.
Post a picture of the entire preamp from above so we can see what caps do what.
My friend Sol recapped Carl's Belles 21A with excellent results, replacing the stock Dayton caps. But 21A has no solid state output buffer like 22A does, iirc, so the caps are doing different things. Your 15uF cap is a big one, so it is coupling something with low impedance, maybe that's the discreet SS output stage?
You basically want to replace the dayton film caps (horizontal with yellow ends.) The electrolytic (vertical cans) are power supply, they are OK.
I personally like Jantsen Superior Z caps for great sound at a good price. Parts express sells them. Make sure they will physically fit before you buy, check dimensions of stock (caps are sized in mm widthxlength.) Some boutique brands are huge. Any film cap that is bipolar, with same voltage rating (250V) and capacitance rating (15uF, etc) will work.
I will check with Sol about which caps he put in Carl's (Mallory, iirc?) I know they were not an audiophile brand, but Carl was thrilled with them even though he originally wanted boutique audiophile status brand. But almost anything will be better than Dayton, except Solen.
Pls post plan view. Rich