Best way to upgrade phone w $150 credit to Evo? Best Buy or Sprint? Store or online?

[WindyCityGirl773]

I have spent several hours on different sites trying to find the best option for upgrading my Sprint phone to an Evo. I don't have SERO, was thinking of doing the employee referral link if it still works.

Currently:
-$150 upgrade credit (I'm fine w/ renewing)
-450ED plan for $69.99 plus taxes
-No company discount (I'm don't work for an eligible company, but I can probably figure out a way to get one. Based on posts it doesn't seem that hard. Although the best way of doing so w/ new contract would be appreciated. For example, sign contract and wait and call customer service, or try to do it when I sign contract?
-Crappy phone for the last week since my Blackberry was fried, so no used phone discount.

I know with Best Buy, I don't have to deal with mail-in rebates, and I pay tax only on the $200, so would prefer to do that. I talked to a Best Buy guy and he said that I put down a $50 deposit, the phone will come in a couple days (the stores order as needed, based on deposits). The $50 will be a Best Buy gift card that I can use towards the phone, so I pay $50 initially then $150.

Sprint I pay $300, tax on $300 (10% in Chicago), then I get $100 as a mail in rebate. The phones are a first come, first serve basis, and the stores don't know when they get them, so I would likely wait longer and can't really handle this crappy phone much longer.

But, can I get the best monthly deal if I go through Best Buy? I am ok paying a higher monthly rate initially (for like one month) and then calling customer service after a week and getting discounts, but if I can only get the best monthly rate by going through Sprint, I will.

Also, what are my eligible discounts? I would like to AT LEAST cancel out the $10 4G monthly cost. Do I get a long time customer discount? First month free? That stuff on top of trying to get the company discount?

Thank you so much for any advice. I am not sure what codes, rates, discounts I can stack and I am not sure if it's the same if I go w/ Best Buy or Sprint.