ProAc or Harbeths?

Boils down to listening room size, preference , type of music you play with.
Best if you can audition both as both will have their respective strengths & weaknesses.
Different people here will have different preferences & different opinions, in the end, what matters the most is what you prefer.
Shortside of things: I heard both in different systems & both sounds very good!! take your pick, BMW or Mercedes ? or Toyota or Honda ?

Wonder if D38 can match Bass of HL40.1 as an 8 inch is hard to do the work of an 12 inches? Which one is easiler to the amp?

Bass of these two speakers are different.
The D38 has a tighter bass but the M40.1 has a fuller, loose type of bass.
The M40.1 has a fuller midrange compared to the D38 for that matter.
The D38 has a more airy, more detailed sound.
The m40.1 needs to be matched w/ the room as this can easily be boomy, D38 not as critical.
Its best if you can hear both side by side as they have a different presentation. Which one you prefer is something you can determine w/ proper audition.

Everyone's ear are different, so get a dealer to loan you a pair and audition them in your listening room. I am partial to the ProAc's since I have a 'British' ear.

I actually have HL5s now and liked it! I would love to have a bit more dynamics. The Bass is a bit loose as well. I have AudioSpace EL34 and Audio Research VT100. Interesting the cheaper AudioSapce matched better with the HL5! More open sounding and better Midrange. I think the ProAc would match the performance of the VT100 better. Wonder if the HL40.1 being more neutral and have better details will do the same? We don't have Harbeth dealers so I just need to ask around and get a lot of opinions!