Those fans it comes with are 2400 rpm so likely gonna make a lotta noise..... is your goal to make them quieter or the CPU cooler....those two goals are mutually exclusive.
Dropping to like 1450 - 1650 rpm will at least let you hear yourself think, but be aware that your thermal performance will be about the same or less than a half way decent air cooler.
Pressure used to be a big thing in water cooling. "Back in the day", rads were like 30 fpi (fins per inch) and ya needed 3000 rpm high static pressure (SP) fans to push air thru the tiny openings. These days most rads at 8 - 12 fpi and 1200 rpm fans have plenty of SP to push the necessary air thru. If ya compare rads by thickness, you will see this borne out as moving from 30mm to 45mm to 60mm thick rads gives single digit % point improvements.
But that's rads as in custom water loop radss.... AIOs are a whole different thing and they normally rely on extreme rpm fans which produce a lot of noise for their thermal performance. At comparable fan rpms, no AIO can outperform the better air coolers (Phanteks, Themalright Silver Arrow, Noctua DH-14) . So again if ya gonna buy two new slower fans for $30 at say 1450 - 1650 rpm, you have basically got a $150 cooler that performs the same as a Corsair H110 or $70 Noctua DH-14.
Now if lower temps is the thing and the noise doesn't bother you say because you wear headphones, then I'd look at some Delta or Scythe fans in the 3,000 rpm and up range.... but you may wake up wife, GF, Mom w/ these buggers