A few thoughts on selecting a QB / WR tandems. A phenomenal Wide Receiver can provide a huge incremental boost to a quarterback.
In 2004, Terrell Owens joined the Philadephia Eagles. The year prior, Donovan McNabb played a full 16 game season and threw 16 TDs. In the 4 years prior to TO arriving on the scene, McNabb threw an average of 19.75 TDs. What happened in 2004? McNabb threw 31 TDs.
In 2007, Tony Romo threw 36 TDs with TO on his team. Is Romo a 36 TD QB? Highly doubt it. Look for him to barely top 25 TDs this year.
In 2007, Randy Moss joined the New England Patriots. The prior year, Tom Brady threw 24 TDs and over the course of 4 years prior to Randy joining the Pats, Brady threw an average of 25.25 TDs per year. In 2007 with Randy? 50 TDs.
Even Matt Cassel threw 21 TDs in 2008 with Randy Moss and Wes Welker.
The above seems to indicate that there is some correlation between how well a QB will do, given a stellar receiver or receiver corps. Given that, look for Kyle Orton to do well this year (if Brandon Marshall plays), Trent Edwards to make an improvement, and Matt Schaub to have a great year. Matt Cassell has his rookie year under his belt and should improve. But his supporting cast, Dwayne Bowe, is a huge dropoff from before (Moss, Welker). Stay away from this guy.
The question remains unclear however - does the reverse hold true? If a receiver gets a better QB, will his stats jump? Certainly good receivers need good QBs (see the difference between Moss in Oak vs NE), but I don't think mediocre receivers become great ones with a great QB. I don't see Devin Hester as a monster with Jay Cutler, nor do I see Bernard Berrian jumping through the roof with Brett Favre.