I agree man the Sound Five are very underrated. On the other hand, if I were Kabuto, I wouldn't really waste my time collecting their DNA except unless I have some. Kabuto had their DNA so he should have summoned them. Unlike the other Edos, the Sound Five would actually be loyal to Kabuto and would have teamwork so together they would deal lots of damage to the army.
Think about it, Kimimaro was keeping up with a Kyubbi Naruto clone while fighting dozens of samurai. Imagine if Kimimaro had the support of Tayuya's genjutsu, sakon/udon's wierd body fusing techinque, Jirobo's earth dome that can suck the chakra from many fodders and Kidoumaro's powerful spider webs.
In other words, if they were summoned as a team, they could potentially kill up to 500 fodders at most. This would help Kabuto and Tobi quite a bit actually.
People say that the Sound Five were beaten by genin. This is true to some extent but those genin were praised to be much stronger than ordinary genin. They were mostly chunin level ninja. Also the Sand Siblings came and gave help so it was an 8 VS 5 battle. They were outnumbered and were low on chakra because they also fought three jounin level ninjas beforehand.
Also Gaara was an elite jounin level ninja during the Sasuke Retrieval Arc (SRA). Temari and Neji were both low jounin level ninja during SRA, Kankuro was a high chunin level ninja during SRA. Kiba and Choji were both low chunin level ninjas.
Naruto with the kyubbi's chakra was also low jounin level in power.