The Bryston B60 is a phenominal integrated amp (I own one), and can fit your budget used. Impeccable build quality and customer support. It sounds very good with Harbeths to my ears.
If you don't mind tubes or not having a remote, the Manley Stingray is a tough integrated to beat. Newer models have a sub out (not sure about management). It's got a great sense of groove (as do many mentioned here) and hypothetically should pair up well with your Harbeths.
If you don't mind tubes or not having a remote, the Manley Stingray is a tough integrated to beat. Newer models have a sub out (not sure about management). It's got a great sense of groove (as do many mentioned here) and hypothetically should pair up well with your Harbeths.