My first thought would be an Opera Consance tube integrated but tubes aren't for everyone. I presume that solid state is preferable i.e. the lady may not want to replace tubes or tube-roll? I've played around with many "budget" integrateds, my favourite is the Primare stuff from Sweden followed by the Audio Refinement Complete. Both integrateds are somewhat soft sounding; slightly rolled off tube-like character to them that would match nicely with the 707's. These amps come up on the used market and fall within her budget.
Best, Jeff