Budget speakers for Orchestral music?

Oh boy that's a tough one! If you had a little more power I would recommend the Brines Acoustic LT-2000 with the (Lowther DX3 driver). It may work well who knows? Speakers like this aren't lush sounding unless the equipment used with them are lush..then you will have lush ;-).Unless you can find them used, they run $1600 a pair new.

The FT-1600 MkII is under your price range and come up used around $500 or maybe a little less.
If you have a small to medium size room. The FT-1600 maybe a good fit. The LT-2000 will be better. The extra cost is for the better drivers and larger cabinet.

The Soliloquy 5.3s or 6.2s should work also.They come up used under $1000. These speakers tend to be more efficient than the specs suggest.

Large Orchestral, 12 wpc, well their not my cup of tea but Klipchorns come to mind.

Orchestral with 12 watts is a challenge, first I would try the new Omega Grands, they are single driver but sound big and have midrange or believe it or not you may want to check out vintage JBLs. They play big sound mostly midrange and up on few watts 102db sensitivity not the best soundstage or detail but you'll get big and loud music from them. I like them but not all the time. They were designed in an age (pre 1965) when tube power was king but there were few units that delivered a lot of power. Problem is that its a collectors market but you should be able to find C38 or 36s with the basic 030 package for about $1200 in good condition. The more magnet (and they used enormous alnicos) you want e.g. a 375 horn (Paragon, Hartsfields etc) the more you pay, but there are some in between the 175 potato masher horns. As I said its not for everyone but for some its nirvana. You can hook them up to a relatively cheap vintage SS with a few more watts and get really orchestral sound but I suppose that defeats your aim. Try the Omegas they will surprise you!

I listen to orchestral music too. Bearing in Qualia's comment above, yr 12 Watts, and Mechans' astute ideas, I would caution you that a 90db spl rating is hardly enough; ~100 is more the ticket. So, Mechans gives excellent pointers.
OTOH, why not consider diy?? Check out the Fostex site and/or melhuish's site (the first is .com the other .org).

You might consider used Triangle speakers in your price range. They mate well with tube gear and are efficient. Current generation I believe are less efficient than previous one. Opera also has speakers in your price range that could work well with a tube amp for orchestral music. As mentioned in a previous post, recreating orchestral music is probably the toughest task for a hi-fi system. At a low price point, there are bound to be compromises. Heck even at a high price point there are compromises.