They are decent units. The Neo Eco has been made by Seasonic while the BP550 has been made by Delta Elecronics, which are very good PSU manufacturers. Anyway I highly recommend you to pay a few more bucks and go for one of the other PSUs. They have a better quality and the price difference is not big.
For example, The COOLER MASTER Silent Pro M600 has a better voltage regulation and noise/ripple supression. It presents Japanese capacitors on primary (by Chemi-con) and quality Taiwanese caps in the secondary (by Teapo).
This power supply provides a single +12V output that is rated for up to 40A (480W) so it is able to handle your 5850 without any problem due to its two (6+2)-pin PCIe connectors.
5 years warranty.
Only 70$ for this PSU is a bargain.
Anyway, If you are thinking about doing CF, I recommend you to go for one of these ones:
ANTEC TruePower New 650W (by Seasonic) (modular)
CORSAIR TX750 750W (by CWT)
CORSAIR HX650W (by Seasonic) (modular)
ENERMAX LibertyEcoII (ELT620AWT-ECO II) 620W (modular)
ENERMAX Pro82+ II (EPR625AWT II) 625W
ENERMAX Modu82+ II (EMD625AWT II) 625W (modular)
THERMALTAKE Thoughpower XT (TPX-675M) 675W (by CWT) (modular)
SAPPHIRE FirePSU 625W (by Enermax) (modular)