Anybody preferring the 507 to anything Stax have ever made must be on crack. They are that bad... Only the 207 is useable of the new Lambdas but naturally Stax could have fixed the recent units like they did with the 009. Haven't bothered to get any of them just to try it out.
You really can't fix any of the drivers DIY. As soon as you open them up they are compromised in terms of dust and debris.