Possibly switching from ATT to Sprint

[RidleyJ329]

ok heres a short background.... I currently have a Sprint account and am using the TP2 with sero. of course i would like to upgrade and get the EVO but cant quite afford it. My fiance has ATT with the iphone 3gs and what ever required plan goes with it. she also has a second line she shares that is not currently not being used so it can be closed. my bill ranges around $35 after tax and hers upwards of $150.

now we're trying to find a way to save money. i have no intentions of moving to att and she was thinking of moving over to sprint. my thought was to open a new line and get the evo while giving her my sero line but i would want to try to keep our perspective numbers to ourselves. the only problem is that she looking at sprints website and kinda has her eyes on the hero

with that said i would have to either get two new plans and see if i could sell my sero plan and do a TOL, open a family plan, or idk if i can get a simply everything line and add a line to share minutes.

im kind of curious of what my best bet would be out of these options or if you guys have any suggestions of your own. either way wed be saving more in the long run. i do also get a 20% discount from work and i know i could prolly weasel a few more discounts out of sprint but dont want to count on them before i commit to anything.

what do you all think might be my best bet to do that might save me the most? please keep in mind that im not one of those types that are looking to get everything for nothing. just want the best best bang for my buck

sorry it was so long. but thanks guys for any response