That leaves you with $9M left to spend on additional pitching (though it could be $4M less if the team's using that higher salary estimation). DanO's been pretty vocal about chasing bullpen help, so that's probably $1M-$3M out of the pie. Dunn may cost more if the team wants to sign him to an extension, based on the principle that you pay a little more up front in order to keep his salary reasonable down the road.
All tolled, that might leave you enough for a flyer on Matt Morris or Woody Williams -- better options than Lidle was last year, but essentially you've got the same club as in 2004. Again that's if the club uses your $43M starting point in getting to $50M and not the higher figure they traditionally use. Either way, I'm not seeing a lot of room for two quality pitchers in there.
Well, if they have $9M to spend after arbitration, using $3M to beef up the 'pen leaves $6M for a starter. That could land a Milton or Perez or Leiber. Maybe Millwood, if Boras gets too greedy and he's not signed on Groundhog Day.
As for the starter acquired through trade, I'm looking for it to be about an even swap of salaries. Position player for pitcher of roughly equal service time and $$, so the budget impact is minimal.