Any expressive-yet-geographically-authentic Sangiovese would work. I would probably tend more towards the Chianti side rather than the Montalcino side when thinking about this, generally. (Though both are great.)
Specifically, my favorite pairing overall is probably San Giusto a Rentenanno Percarlo. Generally about $110/bottle for good vintages. My local Costco has the ‘13 (good vintage) for $95.
My favorite Brunello for pairing with Bolognese is probably Conti Costanti Riserva, which used to be about $110/bottle but is now up over $150 for recent vintages.
Both the Percarlo and the Costanti will benefit from bottle age.
For a bit less I would go with the San Giusto a Rentenanno Chianti Classico Riserva Le Baroncole for about $60/bottle. An equally awesome wine, if *maybe* not quite the pairing would be Uccelliera Brunello — another long-time favorite of mine.
Again, both of these will benefit from some bottle age, though slightly less than the above; and the San Giusto slightly less than the Uccelliera.
I would be willing to drink any of the above wines soon after release with a decant; that just isn’t what I would consider ideal for them.
For $15/bottle, the basic Giacomo Mori Chianti is shockingly good, and a great pairing. Both the San Giusto a Rentenanno Chianti Classico ($30) and the Fontodi Chianti Classico ($35) are good pairings and tasty wines. (The Fontodi is generally about $5 better, so either way.) But don’t discount the Mori; it isn’t *quite* where the other two are, but it is strangely close.
For non-Sangiovese, Giacomo Conterno Barbera Francia ($65) is an amazing wine and a great pairing here. Ditto: Cavallotto Barbera Bricco Boschis ($30). The Cavallotto is slightly less “serious” than the Giacomo Conterno, so in some ways it may actually make for the better pairing. Tenuta delle Terre Nere Etna Rosso ($18) is a steal. (And, yes, Barbera, generally is a great pairing as well. And Etna Rosso very very good.)