$400 for a decent tube integrated is going to be tough. For that price (or less) I would suggest that you look at some great low-powered vintage SS units. The Marantz receivers, mentioned above, are a great choice. I love classic Sansui gear as well. But I think that the best choice might be a clean used (pre-Alpine era) Luxman receiver or (better) integrated amp. Look for a clean L405, L-450 or L-480. All should be available for well under $250.
If you are determined to buy a tube unit, I would look for a Dynaco SCA-35 or maybe an Eico ST-40. Nice units, but they often need work (cap upgrades at a minimum) and can be a bit noisy. If you get really lucky you might run across a Scott 222 or 299 series in your budget.
If you are determined to buy a tube unit, I would look for a Dynaco SCA-35 or maybe an Eico ST-40. Nice units, but they often need work (cap upgrades at a minimum) and can be a bit noisy. If you get really lucky you might run across a Scott 222 or 299 series in your budget.