Nobody can give you an advice in respect of warranty. Even if the board works today it might not do it anymore tomorrow
It is good that you understood that SATA3/USB3 with this board comes at a price. To me it is more an advertisement joke as so many banners on the box... SATA3/USB3 has future. But not with so many ifs. In addition to this hard to get devices at a reasonable price. And SATA3 - too bad that the HDs cannot use this speed today (just for the interface) - only SSD could use it. So what... In the future a board with so many restrictions when you want to use SATA3/USB3 will be pretty useless. Better buy a new one then without restrictions. At least this is what I think.
The memory might require special BIOS settings that it works at the rated speed or in the worst case at all. Look at the Kingston site for information. Also check the manual how you have to enter them (the slots) so that they work. People seem to like not to read this and enter them in the wrong order.
I would not spend so much money on memory but more on the CPU. The additional memory performance will bring you next to nothing in reality.
You should make sure that you have at least two sticks so that the memory can work in the faster dual channel mode. But if you buy more than 4 GB you should have a 64 bit OS otherwise they will be useless. And anyhow - most people do not even use more than 2 Gb with their system. They just think more is faster. That is really true - but only if the software needs it. I run a lot at the moment and I use 1136 MB on WinXP SP3 with 4 GB - this with pagefile (always) off.