It's the absolute best performing "non-extreme" single-pump out there... Better pressure and even flow than a D5 in most loops, and thanks to the PWM, it's just as silent. I never understand people who think they're "loud"... Sure, they make a "water rushing" sound, but only if you don't plug the PWM header in and set up a decent profile!
Currently running an MCP35X2 (which was originally two separate MCP35X pumps that I bought the white MCP35X2 top and HS for), and I get about 1.2-1.5gpm flow through an Apogee HD (one of the most restrictive, yet best performing, CPU Blocks), MIPS R4E Ni/BLK Motherboard VRM and SB Block Kit (two separate blocks), two Heatkiller GPUx3 680 Hole Edition GPU blocks in serial, Heatkiller "Core" GPU Block + MOSFET add-on for GTX650Ti Boost PhysX/Folding card, an XSPC EX420 radiator, an Alphacool NexXxoS UT60 240 and 560 radiators, a NexXxoS XT45 140 radiator, 2x "High Flow" flow rate sensors, 6x in-line temp sensors, and a total of 36 rotary angled adapters and 22 rotary angled compression fittings, about a 50/25/25 split of 45deg, 90deg dual-rotary, and 90deg single-rotary Bitspower fittings.
Tubing is 1/2x3/4 Primochill Advanced, actually have two reservoirs: an EK Multioption X2 150 Advanced that I use both for looks and because having it just before the Dual 5.25 Bay Res helps eliminate the issues that bay reservoirs have with bleeding/bubbles; the MCP35X2 is connected directly to the output G1/4 port of the bay res via BP 90deg single-rotary adapter and male-male rotary coupler.
I tried using two D5's, specifically Alphacool VP655's, and never managed more than 0.7gpm. The MCP35X2 has never once had to exceed "50% PWM Duty" to maintain the 1.2-1.5gpm, either!
Seriously, get the heatsink!!! Also, if you have room, get an 80x15mm fan (I have a Vantec, a Noiseblocker, and a number of Delta/Sanyo Denkei/etc; Vantec is within 2C of the 8000rpm Delta, but is, well, literally silent in comparison).
Without the heatsink, the pump base can get quite hot; over 55-60C. With just the heatsink and only barely a breeze of airflow across it, the PCB temp dropped to 41C max, and with the fan it now has never exceeded 31C! That's basically doubling the life of the pump right there, and for $13-23 depending (single-pump model is cheaper, but you can't use two single-pump models for the 35X2), and $8-13 for the fan, it's absolutely worthwhile.
DDC pumps, unlike D5's, are cooled by air as the electronics are physically separated from and never make contact with the electronics. So, while a D5 can add up to 38W of heat to your loop (or two can add as much as a CPU!), the DDC's like the MCP35X add no heat to the loop, they only help you to remove it!
