I like Westley Richards/they make a very fine gun--thats what I'd buy if I had the cash and were buying new... I dont have the coin for one but, I dont know your pocket book. For pure ROI look for a nice used H&H you can shoot it for 5-10 years and if bought right you will get your money back, not a bad deal..play for free. I bought my first double quite a few years ago a nice english (Willams Evans) 470 shot it for 6-7 years and sold it. I got almost double what I paid for it, maybe not that way now, but english guns are always in demand.
Sometimes a nice FAMARS, Hambrush, or Fanzoj will come onto the market for a good price, they are well worth snatching up! I saw about 5 years ago a nice Hambrush 500 go for less than 11K, it would cost close to 30,000 us to build one now. I saw a Fanzoj boxlock sell in a benfield show for 10,500 US it was a super looking gun but the lenght of pull was short.
Nothing wrong with the K-gun or Merkel too for the price they are good guns. They can be found for well under 10K. Searcy makes some nice guns. I had a 577 boxlock of his for a time, it was a hell of a good shooter, and Butch stands by his product--which is refreshing. His PH grade is a very nice gun with made to order barrel length, LOP, and caliber selection.
Heym makes a fine gun too. Just not real hip on the cocking ind.. at the back of the action, and they are kind of in no mans land on pricing. Most are between 16K-30K.. I'd rather have a searcy for the same to a bit cheaper on the lower end, and I'd much rather have the base FAMARS gun on the Top end, but no question that Heym is a great gun.
VC guns are very nice and I think if I were looking at a mega bore 577/600 I look in there direction. They seem to be very well made...There action is a little boxy for me though.
I'm a died in the wool Blaser fan, and it has taken me a long time to warm up to the S2, but after years of bashing it I will concede and say that I'd own one. I dont like the barrels, and I dont like the push to cock, but the 3 that I've put through the ringer and shot--all were the most accurate doubles I've ever shot. One 500/416 was scary accurate. We busted softball sized rocks out to 75/100 yards with open sight with no problem.
Have fun shopping!
Ed