EL34 comparisons please

Hi, I have a Dynaco st70 which is stock and has the bloomy midrange sound that I like with Jazz. I most recently bought a Conrad Johnson mv52 el34 amplifier which sounds nice and I was thinking of trying some new el34s with it looking for more exaggerated midrange. Any suggetions would be great. Speakers are RSIII Infinity's and the tubes that I am using now are vintage Sylvania.
Thanks,
Guy