Also of note, my ears get pretty hot sometimes just sitting around, does this happen to anyone else?
You might think about seeing a doctor is my advice, lol.
But seriously, you ought to look into studio monitors, like
these things from this aussie pro audio store. Your budget will only allow for a pair, but since you are mostly listening to music, 5.1 won't do you much good for the most part, and spreading your budget out to five speakers and a subwoofer will be detrimental towards that end. Two active speakers with decent bass extension is what I would be going for in a computer setup, that will make your music sound its best. You won't need a receiver with self-amplified speakers, so more of your money will be going to finer sound quality instead of a lot of features you'll never use. Hopefully you have deskspace available, because the studio monitors with decent bass are larger; I would be looking at the monitors with 8" woofers: the Behringers, the KRK Rokit 8, the JBL LSR2328. This might eliminate the need for a subwoofer if you are satisfied with their bass extension, and then you won't need to worry about boominess. You can add a sub later, and cross it over lower than if you had smaller speakers, and this can give you clean deep bass instead of bloated mid and bass where the sub will always draw attention to itself.
If you decide to go the studio monitor route, you will want an an higher quality analogue interface like the Xonar Essence you mentioned, but you can get something cheaper if you don't intend to expand out to a 5.1 system, like
this thing which will do just fine. You do not want to use your motherboard's analogue jacks for a hi-fi music system. Also, if you do think you want some studio monitors, check other aussie pro audio stores for better prices, the one I linked to is just the first google hit that came up with "pro audio australia" search terms. Also, in my experience, you can bargain with pro audio people pretty easily, so if you see something you like somewhere, ask them if they do price matching, or ask them if they can toss in the cables free or something. These people often have a little bit of room to move on the price or the terms of the deal.