A Mostly"tricked out" seraphim squad actually costs 277 points.
9 Seraphim (2 flamers) -w- Meltabombs
1 Vet Seraphim superior -w- Meltabombs, Rosarius, Blade of Admonition, Purity Seals and Plasma Pistol
The Warp Spiders come to 302.
9 Warp Spiders
Exarch -w- tein spinners, powerblades, Withdraw and Surprise Assault
Note that the sisters need to pass an LD test to use thier acts of faith (There is a wargear item that will let them do one automatically for no faith point cost, if you want that in there, add another 25 points)
Oh yes, and the seraphims special move is still a fallback, They CAN be crossfired. It also doesn't work if they are NOT in CC, such as when assaulting a vehicle or if the enemy broke and ran.