Round 1: TPM Darth Maul Vs. NJO Jacen and Jaina. The Solo twins confront Maul at Theed instead of Qui-Gon and Obi-Wan.
Round 2: Clone Wars Darth Maul and Savage Opress Vs. NJO Jacen and Jaina Solo. Fight takes place on the ship Maul and Savage fought Obi-Wan and Ventress in in "Revenge"
Round 3: Same as Round 2 except the setting is Florum
Round 4: Same as Round 3 except its LotF Jacen and Jaina. Jacen is NOT Darth Caedus, has not done any of his evil actions towards becoming a Sith Lord yet, and cannot use his "teleport items" ability. Basically Jacen Solo very early in LotF, c. "Betrayal".
EDIT: Additional Round: Same as Round 4 except it is now LotF Jacen in-between "Betrayal" and becoming Darth Caedus.