Proac Response 1sc or Merlin TSM-SE

This is a very competitive arena. You are bound to get many opinions. I've had all 3 in my home for extended auditions, and have owned the TSM's. The Dynaudios are overrated and not even in the same league. The 1Sc are warm, musical and most fullfilling of the 3. The TSM was most neutral, but then I brought the VSM-SE home, which used the same amount of floor space, but was superior. It is also way overpriced, unless you picked up a pair for 3000 to 3500, but then that would bring you to the 2.5's, which for the size and price are the best. Getting back to monitors, if you want to stick with them (although there is no logical reason to do so) the Tab50 Sig's, and the Tab 2000's are also worth looking at. The nice thing about monitors is that they are easy to audition because they are so inexpensively shipped. It may take months, but the best thing to do is to do lots of auditioning and find out for yourself. System matching is critical.

which of the two speaker can be listened for extended periods of time without listener's fatigue ? What equipment have you used with it ?

Try the ProAc Tablette 2000 Signatures. A bargain at $400 less than the 1SC, they have the same binding posts, the same tweeter, a slightly larger stiffened cabinet, almost the same woofer as the 1.5, and they only come in premium finishes - an option on the whole response line. ProAc calls the 1SC a miniature but calls the 2000 Signature the ultimate in compact loudspeaker design. They could have marketed it as a Response 1.25 and no one would have batted an eye. Expect a full month to break in completely. Truly sublime and expressive.