Either are fine.If you have no intentions on overclocking I'd save a few bucks and go with the less expensive 545 though.There is a good deal on a motherboard with those CPU's over at newegg (a gigabyte 785g AM2+ motherboard) and $20 off.
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.254101
or
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.254105
I was checking it out but on that deal you have to be careful about getting the right power supply for it (it needs the 4+4Pin ATX12V/EPS12V CPU Connector in addition to the 20+4Pin Main Connector).
Another thing that I liked about using a AM2+ motherboard in that combo is that DDR2 RAM (especially DDR2-800) is a lot cheaper than DDR3 although there will be a slight performance loss by using DDR2 RAM.4 Gigabytes of DDR2-800 RAM is dirt cheap
http://www.newegg.com/Product/Product.aspx?Item=N82E16820211188
So 4 gigs of RAM + 545 CPU + Motherboard would be around only $210.98 not bad at all.
One could build a nice budget system using a dirt cheap micro-ATX tower case.
I could see a complete working build under $400. Add a nice $100 graphics card to top it off at around $500 and it will be a kick ass budget gamer.