cary v12, i've used this amp with tyler linbrooks for quite some time now and have no complaints.
depending on the music i'm listening to, the triode setting (50w) has been more than sufficient to drive the linbrooks. if i want to rock (i.e. listening to mahler, bruckner, gov't mule or zakk wylde's black label society) i flip to ultra-linear (100w).
the v12 accepts 6L6, el34 (stock tubes), 6550 (my choice at the moment), kt88 and kt90, so its versatility is extended.
i imagine quicksilver v4's or the new 100w monos (close to your budget new) would be good choices but i have no 1st hand experience.
i used a rogue 88 (not magnumized, about 35w triode, about 70w ultra-linear, conservatively i'm told) before the v12. the rogue was a very good amp and can be found used for about $700-800. it has been replaced with the rogue 90 i think. mark o'brien @ rogue is a stand-up guy, no bs and was nice enough to personally repair a voltage regulator in his sjhop while shooting the !hit with me last summer. you could probably swing a used pair of rogue 120 monos which can be updated to the current 150 monos. check with mark on this, he isn't that hard to reach and always a pleasure to talk to.
also, i haven't tried them myself, but i imagine aes six-packs would drive the tylers nicely. aes is a division of cary and the 6-packs are based on v12 tech. i think they accept different tubes like the v12, but i think they are limited to 50w output. they are $400 over budget new, but used (if you can find them) should be within budget easily. some say they are as musical as the v12 without the flashy look.
"best" is subjective, so take any suggestion with a grain of salt. it would be best to audition any of the amps suggested for yourself.
hope this helps.
happy hunting.