The strings that'll sound best on your fiddle won't necessarily sound best on my fiddle, nor vice versa. Fiddles are individualistic little gadgets--I've had seven so far, all but one built or repaired by yours truly, and no one was quite like another.

With that in mind, I'll put in my own consumer report:

I've mostly used Preludes and Prims, though I tried the Dominant/Pirastro E combo as well. The Dominant/Pirastro didn't do much for that particular fiddle; just made it sound mushy. I should point out, though, that that one had quite a low neck angle, which tends to reduce the fiddle's ability to project sound: low angle = low volume. Preludes sounded very good on that instrument.

A different fiddle also had a relatively low angle, but its voice had different characteristics--on that one, Preludes were too bright; they sounded harsh. Prims took the edge off and gave a nice sound.

My current fiddle has a fine neck angle and volume galore. I have Prims on it, and they sound good, but I'm thinking of giving the Dominant/Pirastro combo another try--this might be the fiddle to do them justice.

All these were medium gauge strings. If you have a low neck angle, heavy strings will increase the downforce on the bridge, increasing the volume a bit. However, most of the (greatly increased) tension runs longitudinally; only a fraction is diverted into downforce. Such strings will be working hard to tear the neck out of your fiddle, so use a lot of care, and shun non-standard (higher) tunings with them. I would be inclined to just reset the neck on such a fiddle and solve the problem that way--my opinion (ymmv) is that heavies only invite repair bills down the road.

If you have a medium-to-high neck angle, stay away from heavy gauge strings--you'd likely be seeing a warped bridge or a cracked top, or both, sooner than you might expect. But if you have that kind of angle, you probably wouldn't be complaining about the volume.

Hope this doesn't muddy the waters too much for you,

JtT