Exactly what comes to my mind. Also if you like an silent build in idle, it won't work because of the pomp noise.
^i second that. Also the fans on the radiator, the do not have any annoying whines or anything (i was using gentle typhoons) but you can definitely hear the air rushing through the restrictive rad.
Closed-loop coolers are just fine for what they are. Some cons would be the lack of expandability and higher temps. But the pros of a closed-loop cooler are much more attractive to me: you don't have to do a 24 hour leak test, you never have to drain and refill it, and you never have to clean it (aside from getting dust out of the rad).
A good closed-loop cooler costs anywhere from $80-$150. A good custom loop will cost at least $250-$350. A cheap custom loop would probably still cool better than a closed-loop cooler, but it wouldn't be a drastic difference and you'll still have all the maintenance that comes with a custom solution. That includes draining and cleaning your loop at least once a year. For me, that's not really worth it.
Keep in mind that this is all speculation, as I've never actually had any experience with watercooling. I've just read about it a lot.
I have an open loop now and ive never had the need to clean it yet. In fact in my experience its just as little maintenance as the closed loop. I clean my computer out yearly anyway, disassemble it get all the fine dust off of everything and reassemble it to draining and refilling the loop would just be part of that process for me, nothing i didnt do already. From my eyes i get easily double or triple the cooling with my open loop with the same maintenance as the closed loop. But you are right its wildly expensive.
I like to keep my PC silent.very quiet
On video cards high end air coolers can be quiter than what youre proposing. Besides you can customize their fan curve. If i let them spin up the fans i never see temps over 60C if i cap the fans at no more than 50% the cards are still very quiet, so quiet that whatever im playing drowns them out, and still dont go over 75C The cards are not overclocked though.