+1 on the power supply. Having a good bit of headroom for future expansion is one thing, but using too little of a power supply's rated power is actually less efficient then having a lower rated one closer to the machine's needs. In other words, it's not as simple as the computer requiring X watts and that's what it is going to use regardless how big of a power supply you install. Power supply's can lose up to 20% right off the top, sometimes more as far as the no name cheapies go. This is where you see the efficiency ratings listed in specs sometimes, an is also where the 80+ etc come from. Also, the load on the power supply effects the efficiency as well, where most well be pretty efficient with a moderate load, and inefficiency is highest with very little or almost maxed load. Bottom line is you could be using a lot more power then you need to be getting too much power supply. As an extreme example with a modest system on a high powered cheap no name psu, you could have a basic system who's components only draw 60watts at normal load, but be drawing an extra 100w from the wall that is lost to power supply inefficiency.
Also with your processor, the i5 may be quite a bit of overkill as well. I guess a lot depends on what exactly you mean by light gaming....as in do you mean light gaming in terms of specs, like console emulators, puzzle type games, etc.....or light as in infrequent, like wanting it to play BF4, COD, etc, just not all day every last setting turned up etc. For current FPS and stuff, I'd stick with the i5 in that case, and of course a decent vid card.....but for like emulators and simpler not dependent on frame rate games and all, an i3 is really about as high as you need to go. Probably even the normal dual core line if DVD ripping is going to be a rare occasion. Also, if you are going to be ripping discs like it's going out of style, that's another reason to keep the i5. Basically what I'm getting at with the ripping is any current cpu will do it fine, it's just a matter of how long it takes. One every now and then is no big deal regardless of how long it takes, but doing that frequently, especially one after the other, it's prob worth something that can get it done faster. Then of course if you are getting the stuff at microcenter, they don't always have bundle discounts on i3 but always do on i5, so if that was ever the case and the i5 is right near the i3 due to that, then of course get the better one.
Motherboard.....first and foremost, get a brand you are comfortable with that has the ports and all you want. Beyond that, don't be afraid of the lower end boards of your favorite makes if they have the ports and all you need. Remember this is an HTPC and not a normal desktop gaming rig, so a basic board is usually sufficient vs one with fancy overclocking stuff and all included. Overclocking an HTPC doesn't do much for you and just potentially creates extra heat meaning extra noise to cool it vs what it could be.
RAM.....same idea here too. Low latency performance ram isn't going to do much for you in the HTPC world. You don't need anything fancy other then quality stable stuff. Often times, performance ram is just as cheap as normal series quality ram, so by all means in that case....but if you see quality brand normal ram cheaper then performance ram, just get the normal stuff.
Basically that is all just some food for thought and not meant to discourage any of your selections. HTPC functions are one of those good enough is good enough and overkill isn't going to give you much tangible benefit things unlike a typical desktop/gaming machine. IMO effort is better spent on more tangible benefits like making it as quiet, efficient, and cost effective as possible vs squeezing out the most performance and having lots of headroom. Also by cost effective, I don't mean cheaping out and spending as little as possible either, rather simply getting the level of parts needed for the job....and say if you were trying to stay in a particular budget, getting the right parts for the job could mean rather then having too much overkill inside that case that isn't going to do much for you, you could get an expensive nice looking case you wouldn't normally spend as much on...that sort of thing.