WifeMpls might kill me for this, but while I was poking around in Expedia's hotel bookings I spotted one a bit north of the Plaka, dirt cheap & with pretty good reviews, so I booked it: Hotel Aristoteles, $30.76+/night, $309 all in for 9 nights, prepaid, includes continental breakfast.

A couple others that caught my eye:

Airotel Parthenon (where we originally were going to stay), $85 (+$10 taxes) for stays of 3+ days in Expedia

Hotel Novus, new 4* w/ really good reviews, $75+ (w/ "Fee Chop") in Priceline, not clear if cheaper rates include breakfast. Expedia offers $79+ (apparently no brekkie) & $89+ (w/ brekkie) for Hotel Novus.