I see. Looks like the standard one with non-reference cooler. But really, the
only performance-related difference I can see between our two cards is that mine has an 875Mhz Core clock where yours has 850MHz. You could probably OC your card easily to where mine sits at (although I don't know this for sure, just speculating). Is 1680 x 1050 just really not working for your taste? I was just so (pleasantly) surprised to learn that game was so well optimized when it launched. I thought I would be stuck with like 1280 x 720p on Medium at best, before I finally got it home and saw it could handle better. But. I do agree that more is certainly better.
In fact, I'm looking to replace my 4890 with a 6950 2GB, GTX 560ti, or better when I can scrounge the cash together. Heck, I'd settle for a 5870 or GTX 470 if I found a nice deal on one. The lowest I would personally go for an upgrade for myself would be a 6870 or a GTX560; and that's only if I find myself really too strapped for cash to find a good deal on a 6950. In that event though, I don't think it'd really be worth it, and better to just save up a bit more cash if I'm that close and just get something better. The thing is, these 4890's sit in an awkward spot right now where they're sufficient enough for maxing out most mainstream games available (COD, Dead Island, etc.), but lack DX11, and aren't enough for getting absolutely all the eye candy out of the more demanding titles out there (Metro 2033, Witcher 2, BF3). Unless you have the money to get a DX11 card in the GTX 560 or higher range; or HD5870 or higher range, it really won't be that much of a performance increase over the 4890.
They have this XFX 1GB 6870 going for $149.00 USD after mail-in rebate w/ free shipping at the 'Egg right now:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814150561 . Also comes with a coupon for a free copy of DIRT 3, which could be a plus if you're into those kinds of games and don't have it already. The cheapest I could find a *used* HD6870 on ebay for the Buy It Now price was exactly what you would pay for that new one from Newegg, minus the warranty. A word of caution, though: those negative reviews on Newegg I checked out for this card seem to be aimed at how hard it is to get that rebate, so I'd definitely look into that first. If you look on that chart you posted, it seems the 1GB 6870 handles BF3 pretty well, but I don't know how it will hold up to the resolution you want to play it at. Check here:
http://www.overclock.net/t/1128191/6870-battlefield-3 . That one's on Ultra Quality settings, though. I'm sure just High would yield better (i.e. playable) results. I've also heard around that if you're going to go with a 6870 from XFX, get the one with the dual-cooler design if you can find one or one with a reference design (for instance, your non-reference 4890 has the SKU beginning with "HD-489X....", and a reference HD4890 from XFX would have something like "HD-489A..."). And of course, you'd also have to upgrade a bit sooner (yet again) than you would have to with the 6950 or higher. I'd recommend that if you're going to go, however, it'd be best to go all the way and just get something you know is worth the trouble and will hold you over for a good time to come. But that's just my own personal opinion.
Also, a bit of bad news - unless you have someone (like a friend) that will buy the 4890 for 100 dollars, you more than likely won't be able to fetch that much for it on a place like ebay. Most of those are selling for anywhere between 60 to 80 dollars max these days. For instance, some guy has a listing active right now that features TWO 4890's going for $165 Buy It Now price, with $145 for both as the starting bid. I bought mine for $75 shipped about six months ago. I'm not saying it can't happen (you may be lucky), but it may be a tough sell if you take it to the auctions for that amount with so many others on there listed for (significantly) cheaper.