Kar Vastor and Sora Bulq vs. Darth Sidious...
...One Royal Red Guard and Commander Thire. Kar beat Mace once and lost to Mace once so he is somewhere around Mace's power so he's probably somewhere around Sidious's power (I'd say a little weaker). Sora is a bit further behind Sidious in terms of power, though alone he could last a little while. The Royal Guard is a very minor threat to either Kar or Sora. Thire is a bigger threat than the Guard. Thire was the Clone who found Vader on Mustafar and was leading the search for Yida's body. He is an ARC trooper and a Shock Trooper. He lead the battle on Courscant, alone with Commander Appo, when it was invaded by Grievous.
Still, Thire wouldn't be to much trouble for someone like Sora or Kar. Together I'm sure Kar and Sora'd beat Sidious. But this battle could go several different ways. Depending on how it played out either team could win, IMO. However, I'd give tha advantage to Kar and Sora. But it depends on how it goes.
1) Sora vs. Sidious while Kar fights Thire and the Guard. This depends on if Sora can hold off Sidious for long enough for Kar to defeat Thire and the Guard. I'm not sure about this one.
2) Kar vs. Sidious, which would depend on if Sora could defeat the Guard and Thire before Sidious defeats Kar. If it went like this I think Kar/Sora'd win.
3) Sora vs. Thire and Sidious while Kar deals with Guard. While Kar'd beat the Guard in about 3-5 seconds Sora'd have to put all his concentration on defeating Sidious and would probably get shot from behind by Thire. Then Thire and Sidious'd beat Kar. If Kar was the one fighting Sidious and Thire Sora could probably beat the Guard in 4-8 seconds. Kar could probably hold Sidious and Thire off for that long for even if he got hit he's tough enough he could probably plow through his pain.
4) Sidious and Guard vs. Sora while Kar fights Thire or Kar vs. Sidious and Guard while Sora fights Thire. Not sure about this one.