In the way of wages, we should be able to spend lavishly after Rio, Vidic and Giggs' departures. Going off of reputable reports, that is around £250K trimmed off of the playing staff wage bill, so in that respect we should have no problems offering high-end wages. But whether we would decide to spend any transfer fee in excess of £40M is another question.
Personally, I'd like to see the centre back we sign as someone who has amassed plenty of appearances internationally and for his club, while also having experience in European competition and domestically. My preference would be Benatia or Garay even if they are lesser talents than Mangala. Among Smalling, Jones, Evans and Benatia/Garay, we would have a good spread of ages with some in their prime and some approaching that with plenty of potential.
It isn't absolutely vital of course and as the old adage goes, 'If you're good enough, you're old enough', but it would help the transition of our defence over the coming years, rather than having experienced stalwarts all leave at once later down the line, as Rio and Vidic have this season. We have a young enough defence as it is and with Shaw likely to join and de Gea and Rafael also figuring in our back five, we only really have Evra and Evans as experienced defenders.