Well, Hi_hifi, it has been almost two and a half years since I posted on this thread, and I for one, would be curious to know which way did you go? 300b or 45's. If you read this please send a response.
By the way, I still have my Jeff Korneff 45SEi, which gets a lot of play time and I have not had a good reason to replace the National Unions 45 I got it with. Some day, $$ permitting, I'd love to try the EML mesh 45's.
A year and a half ago I replaced the Fostex drivers on my BLH's with Audio Nirvana's Super 8 Cast Frames. The dynamics, instrument separation and soundstage, especially for their meager price are unreal.
Happy listening.