I echo other people’s thoughts and recommend waiting. They don’t have an immediate use, except Moltres for beating Tangela / Breloom solos (Tangela is a hard solo, but Breloom is considered easy). Moltres would also require a charge TM to obtain Overheat to be worth its meat compared to non-legendary attackers like Blast Burn Charizard or FS/OH Flareon. Entei should be out of the question since it has less DPS than Moltres and yours also lacks OH.
Raikou is good but not currently useful and out-DPSed by Electivire. Both Raikou and Moltres may potentially be outclassed by Zekrom and Reshiram when they are released in 5th Gen.
Zapdos is both out-DPSed and out-TDOed by Raikou.
Keep the RC. Depending on their movepools, Darkrai, Zekrom, Reshira, Kyurem, and Thundurus may all potentially be strong RC candidates due to potentially having the best DPS for one of their types.
Moltres has the highest DPS for a Fire-type attacker with Fire Spin / Overheat.