Here is a campaign slogan I would recomend for the Rockies...

Chicks dig the long ball
Joe Koshansky '08

These are interesting stats especially because they are fairly reliable in predicting run production. What is interesting is the Rockies have a huge potential for creating runs and it got better in the off season. Run production usually translates into wins but last year the Rockies did not win as many games as their run production would have predicted. However this year I think one of the highlights of their off season will be an increase in next years run production. I predict that the Rockies will make significant gains in OPS at a number of positions and will not lost too much at any position.
First base- A lot of people have been jumping off Todd Helton's ship but I think this year he will return to the Todd Helton of old. First of all he should see more pitches due to the success of Holliday, Hawpe and Atkins and hopefully will be healthy this year. If he returns to normal he will probably have an OPS of .950 or better which obviously will raise the Rockies first base position OPS.
Second Base- I see no reason to beleive that Jamey Caroll will see any substantial declines in production. Along with that having Matsui back up Caroll will probably see higher returns than having Gonzalez back him up. The second base OPS should remain close to the same as last year.
Shortstop- I don't think Tulowitzki will win the Rookie of the year award or have an outstanding season. His strongest point is that he is replacing Clint Barmes therefore he will have a high Value Over Replaced Player. I figure Tulowitzki will have a good year and should increase the team OPS in this position by about .150-.200 points. Therefore the Rockies should make huge gains in terms of run production at this position.
Third base- I figure Atkins will have another outstanding year by OPS standards. He will probably remain in the top 5 in the national league.
Catcher- This will probably where poor managing will hurt the Rockies the worst (finishing close to how much they will be hurt by bullpen mismanagement). Ianetta is my personal favorite of the Rockies prospects. I rank him above Tulowitzki especially in terms of immediate impact. Unfortunately Ianetta will probably not see much more than half the starts at Catcher and the potential gains made in OPS will not be realized because Torrealba will bring down the position average if he gets close to half the starts. I predict that Ianetta will have an OPS above .850 and Torrealba will be somewhere around .700. This means that the Rockies could increase their OPS about .150-.200 at the Catcher position if they started Ianetta at least three quarters of the time, but they will probably only increase it about .100-.150 with Ianetta starting half of the time.
Left and Right field- Personally I think Holliday had a career year last year partially because Helton was pitched around and he was pitched to, but I don't think he will decline a great deal. Neither should Hawpe. They will both probably have pretty good years but I think it would be pretty optimistic to think they will both finish in the top 2 for OPS. Look for top 4 instead at both positions with no substantial decline in OPS.
Center Field- This is the only position I would say the Rockies can expect a decline in OPS. You are right that Sullivan is a serviceable center fielder and was not an emergency to fill. However Center Field was the position that they could gain the most at by making a trade or signing a free agent, because of the lack of big league ready prospects at Center Field. Shortstop and Catcher were the biggest holes last year but they are filled this year by prospects. But they will probably lose OPS this year because of the trade they made for Taveras. Taveras will probably have an OPS around .700 where Sullivan and Co. were at .744 as you mentioned. A couple of options: they could start Spilborghs who posted a .768 OPS last year in Center but they would give up some defense. Or they could execute a trade. My personal favorite center fielders would be Grady Sizemore of the Indians or Rocco Baldelli. Both of these players would be likely to increase the OPS about .100 from last season. But both would cost a pretty penny. Baldelli in prospects (that we have and could get) but Sizemore might be untouchable. With the recent trade we have a surplus of young unproven pitchers. With Bucholtz, Hirsh, Jimenez and Morillo as pitchers and Baker, Stewart and Taveras as fielders, we could come to a package within these players in which we could probably receive Baldelli in return. The Rockies have consistently made moves for the future and it is time they made a deal like this for the present.