In summary, @dreamingspires asked how you can follow more Twitter users without feeling overwhelmed with updates.
I only follow around 60 people on Twitter who in general do not post very frequently.
However, I follow more Twitter accounts in Google Reader which is actually nicer because I see the tweets grouped by user and I can use tags/folders. TweetDeck has groups but Google Reader is more efficient, it also has better search and saves all tweets. In addition, Google Reader is available from any Internet-connected computer while the current version of TweetDeck is only desktop-based. Seesmic has a web version but Google Reader is more efficient.
A screenshot of some of the medical Twitter feeds I subscribe to in Google Reader.
In short, you can expand the number of people you follow on Twitter by subscribing to their RSS feeds in Google Reader.
Currently, there is no tool that works better with large inflows of information than Google Reader in "condensed" view. Try switching the view modes in Google Reader by pressing the "1" and "2" keys.
@dreamingspires was concerned that interacting was not possible with the RSS feed but in fact it takes only 2 clicks - click on the tweet in Google Reader, which opens the Twitter page, and then click "reply".
The circle of online information (full version) (click to enlarge).
How to deal with the information overload from blogs, RSS and Twitter