The least expensive 27's that will approximately display Adobe RGB are the Dell U2711 at about $950.00 (USD) and a DoubleSight Displays DS-277W at around 1050. A NEC PA271W-BK will run around 1270, and with a calibrator, around 1580. An Eizo Flexscan SX2762W-BK would be about 1550, and around 1660 with the calibrator. A Datacolor Spyder4 Elite calibrator for the Dell and DoubleSight would be 249. The Dell and the DoubleSight have 3 year warranties, the NEC, 4 years, the Eizo, 5 years. All are 2560 x 1440 resolution. And, in my opinion, all should all do a great job with what you are trying to do.
Tony