I am very happy with my GA-MA785GM-US2H. And my computer needs sound very similar to yours - My primary uses are MS Office, Internet and basic graphic editing and design. I play only one game, the MS series Age of Empires and it doesn't tax any system made in the past 4 yrs!
I'm quite satisfied with the built-in graphics of this board - heck, I reduce the memory devoted to it from 512MB to 128MB to give myself more memory in Windows. I run a 22" wide-screen in 1024 mode - if I used a higher mode I might want more RAM for it. Regardless, all is fast and slick from my viewpoint.
I use G.Skill 1066 "Pi" DDR2 RAM - which is actually rated at 1100MHz. I chose this RAM after going thru 2 other brands, learning a lot along the way - and I've been helping others since to avoid my errors. Here's the lessons.
1) Get RAM that doesn't require much over the "standard" voltage. For DDR2, this means 1.8V-1.9V RAM. Also, don't trust the specs for RAM listed on a sales website - always verify the numbers at the mfg's website.
2) Get the lowest latency possible at the speed you want to run at - while keeping an eye on the cost. For 1066 this means a CL=5 and for 800 this means a CL=4.
G.Skill is one of the best brands available. I actually run mine at the base speed of 800 rather than 1066. The reasons for this have to do with the lack of real speed throughput differences between those two speeds once you take the CL/Latency/Timings into account. You'll find many folks here willing to argue about whether it's worthwhile trading speed for latency and such, but the fact is, outside of the rule of looking for low latency at a given speed, the settings you choose is pretty much a personal choice. I "feel" my system runs better at 800 rather than 1066 but the 1066 RAM has the features I wanted! And yes, I know this isn't really clear!
As for the limitation of AM3/AM2+ socket boards. Here's how I understand it. The AM3-only design allows the use of DDR3 memory and faster RAM choices. The AM2 and AM2+ uses DDR2 memory and is limited to around 1200MHz speed - but generally you see a max speed of 1066. When you make a board that lets you use the full line of both AM2+ and AM3 processors, then you are using only DDR2. And in addition, you are limited to only 2 modules of 1066 RAM running at 1066 speed.
As mentioned above, being limited to running 1066 memory at 800MHz if you have 4 modules is not a real handicap. You'll gain the benefit of the faster latency by running them at 800 anyway. But to some, the idea that you don't get to make your RAM run at its fastest is a negative. In reality, 95% of users never have any idea how fast their RAM is running and don't really suffer too much because of it.
Here's the RAM I'm using. G.Skill F2-8800CL5D-4GBPI
http://www.newegg.com/Product/Prod [...] 6820231194
And here's another G.Skill RAM I'd recommend. F2-8500CL5D-4GBTD
http://www.newegg.com/Product/Prod [...] 6820231270
Here's a list of G.Skill 1066 RAM. Of these, I'd only recommend one - the last one which requires only 1.8V. Note the voltage requirements of the others range up to 2.1V. 2.1V is the max voltage of my Gigabyte board and many others. In addition, when you push more voltage into RAM, it tends to make it run hotter, draws more power by definition. And most would agree that RAM that need more than "normal" voltage isn't high-quality. It represents a lazy way to increase the specs of the modules, pushing it to limits of speed and latency it may not have been designed for. Intel has put the hammer down on higher voltage DDR3 RAM for its i5/i7 boards because they say the higher voltage to the RAM can affect the life of their CPUs. But no such rule for DDR2s is in place. But most makers are coming up with lower voltage because of its advantages - note the red "Low Voltage 1.8V" marketing blurb about the last G.Skill in that list.
I can't recommend ANY Corsair XMS or regular DDR2 in the 800/1066 range. Almost all require 2.1V and the ones that don't have higher latency. Corsair is one of the brands I returned before getting the G.Skill. (Update - as noted below, Corsair XMS does have a 800 module with 1.9V so I can recommend it.)