Wow, there sure is a lot of unsolicited advice being dispensed here.
OP, enjoy your HD650s. I love the sound of my HD600s. Some disparagingly call them mid-fi, and that's just fine. They can coat whatever equipment they want in platinum and enjoy the sound 0.5% more, or maybe (in many cases on this forum) just have the satisfaction of having spent a lot more money on it. If you want to upgrade, there are options. If you're happy, be happy. It's all good.
People have hinted that there there was a revelatory moment in their headphone hobby - and I think the HD 650s are mine. Sure, the Grados were a step up from the really bad cans - but I wasn't expecting the hyper-leap forward between them and the HD 650.
Edited to add: I once used to wonder how people could pay $200 for a meal. Then my ex-girlfriend treated me to a meal at a middle-end restaurant in San Fran - it was a 'homestyle' type of weird 'gay restaurant' where her friend worked (had never heard of restaurants based on sexual orientation, but whatever). I had a chicken with mashed potatoes and gravy type dish - it was just as revelatory! I no longer wondered how anyone could pay that much for a meal!
This pretty much nails my experience on the head. I've had a total of three such instances in which this eureka moment has occurred. My first revelation was the pair of HD280s my parents got me for Christmas. The music just sounded so incredibly smooth with no bloated bass or extremely exaggerated treble. I didn't realize music could sound like that. $100 was a heck of a lot of money for a college student so I was happy with these as my only can.
Well, at least until I started reading on here and decided to try other cans which was eventually led to the AD2000, D2000, K701, T50RP, HD650, RS1, and many others. Each of these cans was a different revelation in sound. One had better bass definition (I didn't even know this was possible), the D2000s had incredibly flat bass, the SA5000s and T50RPs raw speed, the vocals of the AD2000, the soundstage of the K701, the tonal balance, the mids, and the treble everything was better on one or the other. However, I was perfectly fine stopping with one of these cans and calling it quits.
Then I went to a meet just to see if it could get any better. I had the misfortune of listening to almost every high end can. It was breath taking everything sounded so good, so right, so clear, it was scary. My setup didn't really hold a candle to these things. I remember the trip back I couldn't play the Bose stereo in my dad's car because it sounded so terrible (that's never happened before). That's why I upgraded to the LCD-2 even though as a college kid I don't have the money and I have to pay my own way through school. It's worth it to me as all of the traits I desired from other cans are present here but I can certainly see how the improvement wouldn't be for most people. I'm still struggling with the cost of these things and don't know if they'll be keeping due solely to their pricetag.
I really don't understand why everyone is going off the deep-end when a couple of people have made faux suggestions about an "upgrade path". I honestly don't think too many people are serious about it as it's in the nature of HF. Also I don't think anyone is being pretentious with their audio gear, I know I'm not.
@OP: Sorry for the long post. I hope it was worth the read instead of a snide and dismissive TLDR. I for one feel that if you are enjoying your current system do so for as long as possible before upgrading it or don't upgrade at all. It's honestly not a bad final setup to have.
I felt the urge... though I'm just messing with you.