5k+++
Someplace is selling

HD800 from what I can gather online:
http://forum.lowyat.net/index.php?showtopic=1855460&hl=hd800 - RM5500
http://www.lelong.com.my/merchant/default....2&show=List&P=1 - RM5599
http://www.lelong.com.my/Merchant/default....antCategory=All - RM5799

In my opinion, I don't think that the hd800 is like the hd650.  The signature is different, the hd650 to me feels laid back and warm, whereas the hd800 is more detailed, neutral and has fantastic imaging qualities.
 
As to how it fares against other high end cans, which models are you referring to? At that level, it's mostly about preference as all the models sound good.

p.s.  I have heard that the hd800 requires a very, very GOOD (read, mahal) amp to really make them sing
As always, try them out EXTENSIVELY if you plan on buying em....rm6k ain't cheap

Just my humble 2cents and should be taken with a bucket of salt.  I believe there are some hd800 owners here that can give you a better review

Pretty much, that's not even including the amp! 

Like duh2k, I too have heard that the HD800 is difficult to drive.

Yep, be prepared for a big hole in ur wallet to get the maximum potential of the HD800. They are one of the most picky cans out there. 

Well, I'll be very honest here, I am somewhat ashamed.
While there is absolutely nothing wrong with going to the top flagships right off the bat, there is ONE fatal flaw doing so:

You will not be able to fully appreciate it.

This is true and can applies to many other things.

Anyway, back to my experience.
My first reference is AKG K701 and I am stunned by its capability to produce the high, it turns an absolute basshead like me into one who appreciates high/trebles, it also made me hating low quality bass (muddy and overwhelming).

Then I found a good deal on HD800, pulled the trigger, and I am in another level of world now. I love the neutrality and imaging HD800 produces, it is an absolute perfection of the AKG K701. It is undeniable that K701 is a flawed headphone though, thus the cheap price. HD800, in a nutshell, is a fixed AKG 701 in almost every aspect. Fuller and better bass presentation, balanced treble and they are all very well controlled.

I've always thought and felt that K701 is the start and the end of my journey, until I've gotten HD800, all of sudden, I felt that my journey has just started. HD800's neutrality sparked the curiosity in me, the curiosity to find out the vast definition of "coloration" of many headphones.

With all that said, I still like K701, it has something HD800 don't have and vice versa. The flaw of K701, uncontrolled peak high and lack of imaging is the major turn off for most people I guess. It is very left and right, while listening through HD800 feels like I am listening to a pair of speaker, not headphone.

Now..I can't talk for shit because I don't know shit. Above is just my opinion comparing HD800 with K701.

Fun Fact : I can get both HD800 and K701 with Rm6000 with some changes enough for me to buy a cheap mid entry level amp (ie, Fiio E9)

naw im not in a hurry for flagship headphones. after all, i still prefer speakers even with my AD900. and i have all intentions for my AD900 to be the end of the line until i am done with ALL my other "goals" and "wants"

and that will take quite a long time (at least 4-5 years time span)

To me, yes, it's a different league

If I'm not mistaken, Beyer's T1 and Denon's D7000 are around that 5k-6k price range.....Against other neutral cans; well, they certainly beat Sony SA5k's which are considered quite neutral.  Considering the price you pay, they better damn well beat my pair of cans

rm6k.....that's like 1 year worth of chicken rice man 

hd800...

i actually like the fit of the headphone.. very easy on the ear oso their sound.. but too airy and not enough solidness in the sound. probably will need a 'specific amp' rather than a  powerful amp to drive it.. also a very good dac perhaps, to improve the imaging..
cant afford it tho, and aiming for other things s well..

Now here is where the problem comes in, I can' tell.
What is perfection?? I can't tell shit lol.

Reason is simply because I have never tried the low and mid tier headphones, proper one anyway.

Price of HD800 could vary from 600GBP to 999GBP.

Perfect is too subjective a word to be used in the context of audio quality. I'm sure you know that every individual hears differently and each have their own taste in what they listen to in a pair of headphones. Some cans will sound perfect to them but not others. Despite having said all that, I'm just gonna contradict myself by quoting Mike from Headfonia.

"As the flagship STAX headphone, the Omega2 is the most perfect headphone I’ve ever listened to. All of us can start from different headphone preferences, and ultimately we would end up with the Omega2 as the ultimate end of all headphone. At this level, there is no more dynamic vs electrostatic debate. The Omega2 reigns supreme at the top of the food chain."