Try this thread for some ideas.

if I had all the attachments I would stick with ryobi, troybilt, or any brand that takes the quick link attachments. why by 500 dollars worth of attachements just to get alittle better brand? better yet check out ebay I got a 4 stroke for 15 bucks, but the shipping is sometimes kind of step which ups the price to 30 to 40 bucks sometimes.

I have the Troybilt TB475 with 25cc 4 cycle. I like it well enough. I think Ryobi has the exact same trimmer in HD.
It has been more reliable than my $420 Honda trimmer!!! What can I say!!! Unless you treat it as toys, then you buy a complete new and better set just for the fun of it. Otherwise, just get the 4 cycle power head. Particular if you just use it for home use. I beat it up pretty hard for 3 years, now is still hanging in my shed.