The mobo, CPU, and graphics card should all work well together.
For the mobo though, I think you should consider getting one with UBS 3.0 built in to speed up doing quick USB backups and other USB functrions.
The HD5450 is a good HTPC card for its price range and is recommended at that price here:
http://www.upgradevideocards.com/nongaming.html
But note its poor performance for gaming - even for light gaming. What are your intended uses?
The power supply I could find little about, but know it is not a strong brand. Power supplies are not a place to scrimp on a system - keep in mind that it is the electricity powering the whole system - like buying a nice car with a great style, a nice interior, good drive train and handling, then skimping on the engine.
400 watt is more than enough to power your system and allow for a little expansion later - but not a real serious gaming video card. This Antec Basiq BP430 430W at $30 after rebate would be acceptable:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371023
Although the Antec Earthwatts Green 430w at $45 after rebate would be better:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371034
Both will still allow only a limited video card upgrade later. They will allow a step up to a decent mainstream gaming card but not a powerful gaming card. To keep that option open you need to move up to a 500w or greater PSU.
For only a little more, $50 after rebate and $6 shipping, you could get this excellent 500w PSU:
CORSAIR Builder Series CMPSU-500CX 500W
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139018
For the memory, you need to identify the make and model to receive a review of it. Some DDR3 will work in your system and some will not.