Since you use a low powered tube amp it might be best to check out speakers that are an easy load on the amplifier.Soliloquy 6.3s or 5.3s come to mind.They both have great bass and the top end is a tad more extended over the Shearwaters.Also you have Coincident and Silverline speaker lines both tube amp friendly.You could go with monitors and a sub.The new Eminent Tech LFT 16 should work with your amplifier.The eminents have a 3 position tweeter setting.This way they can be tweaked to your needs. The site qoutes $950.00 new but you maybe able to get them cheaper through a dealer. Add a subwoofer like the Adire Rava and you should be in business. Once you become accustomed to sealed bass it will be hard to go back to anything not sealed.
Good Luck!
Good Luck!