To keep the cost reasonable, you could put the reservoir on/in the radiator, not the pump, and since you are going to need a radiator anyway, it might work out less expensive than putting a reservoir on the pump.
I not researched the matter of how quiet the pumps are in depth lately, so can't answer your question from recent experience. All I can say is that in my recent and past search of reviews of the pumps, and forum entries, it seems that the comments about the pump being good and quiet are more numerous, by a quite noticeable margin, for the Laing pumps.
For what it is worth, way back in the early 1970's, when I was in my mid teens, I was very into the hobby of keeping and showing tropical fish. I really needed a life back then. At that time the Eheim pumps were quite a status symbol for any aquarist. I never had one, couldn't afford one. They were expensive and performed pretty well. They were no quieter than most other high-end water pumps of the day. Their reliability was about the same as most other high-end pumps, maybe slightly better.
The Eheim pumps are older designs than the Laing, and, if I am reading the specs correctly, the Laing pumps have higher flow rates, and higher head specs. The Laing pumps, with their higher flow rate, can be undervolted for smaller cooling systems, so they are quieter, if the full output is not needed. The Laing DDC pumps are also much smaller than the Eheim pumps, which makes it easier to find a place to put them and a way to quiet them down.
That is what I have found out, and more or less believe, and I may be way off. Only SPCR does the kind of noise testing that is worth a hoot, and they haven't ever tested the two pumps. Also, I think that like almost anything about acoustic perception, your individual expectations and biases are going to have a big influence. In other words, psycho acoustics play a very prominent role.
All that said, I do have experience with the Laing/Swiftech DDC Pro/MCP 350, and can vouch for how quiet it can be. And, mind you, mine is in an aluminum case, a big aluminum case (think lots of big panels that can vibrate and transmit noise), yet when properly isolated it is perfectly quiet.