Any monitor with an IPS (in plane switching) panel would be a great start, in fact it's a must. IPS panels provide accurate colour reproduction at wider viewing angles.

I use a Dell u2410. 24" IPS monitor. It comes factory calibrated to adobe rgb and it's very close. I use a spyder express colour calibrator and the factory settings are almost identical. It's far cheaper than many monitors with the same specs, has been very reliable for me for a while now.