The iRhythms C491 is a clearly then a nice little iPod speaker package but the final verdict depends on how good they sound. Well, on the whole they sound pretty good, though somehow it's easier to talk about its shortcomings rather its strengths. The sound stage is inevitably quite narrow due to the small size but the biggest issue is the lack of bass - there's just not enough.
It makes for a much thinner, slightly weedier sound than you get from the Logitech's or the iHome's. It also suffer's at higher volume, sounding a little strained. On the plus sound, it's a reasonably accurate, natural sound and much brighter than the Logitech set, though that is down the lack of low end. Vocals sound great, though, and if it could match the Logitech's for bass, it would be the better set sonically. In the real world though, its small size means it doesn't match up. It's not a set for long term listening then, but as a travel set it does its job admirably.
Ultimately, for Â£50 it's a good buy, but in terms of looks, and sound quality the style the Logitech's have it beat - though they should do for double the price. Feature wise the iRhythms lack the ability to control the iPod from the remote but makes up for it by having an S-Video pass through, which the Logitech's don't. If you think that you might need that feature when you're travelling then it could sway you into spending less, though you'll have to weight it up against the lower sound quality.
Both these speaker docks make good cases for themselves. If you were to base a decision purely on sound quality then the Logitech Pure-Fi Anywhere set wins the day, with its more musical tone and more pronounced bass. However, the iRhythms A491 is still a decent sounding little travel iPod speaker set and though it doesn't have the style, build or bass of the Logitech Pure-Fi Anywhere set, it does have video out and is also half the price.