I THINK the HM model is just the one released to Asian markets,
or you may be thinking of Dell UltraSharp U2312HM 23" which is a different monitor
what do you want your monitors for? always try to match in brands if going multimonitor, if you are moving to eyefinity in the future the bezels on dells may bother you, they dont me. debezelling can help
U2142M is a great monitor and i think Dells really are the cremedalecrem in monitors.
U2142m offers a great IPS screen with pretty good anti glare, it has a decent 8ms response time. 60hz ofc, its and 6bit+something panel so colour reproduction should be pretty good
also 16:10 master race those extra 120PX really make a difference
Stand allows lots of rotation and adjustment and IMO dell stands are some of the best on the market. and id put them on any monitor, also build quality and warranty are excellent.
or theres the U2410 used
u2410 has a slightly high response time and uses H-IPS instead of S-IPS, some say this is a better panel for design work as it is true 8bit
buying used is always great
dell u2412m on amazon.com
http://www.amazon.com/Dell-UltraSharp-U2412M-LED-Monitor/dp/B005JN9310/ref=sr_1_1?ie=UTF8&qid=1367501322&sr=8-1&keywords=dell+u2412mbuying used will be a far better deal and i think warranty transfers between owners, even if you dont have the docs. ussually a 3yr warranty
also consider with the extra money getting a second monitor
alternatively literally just over budget for this one consider the u2711
http://www.ebay.com/itm/Dell-UltraSharp-U2711-27-LCD-Monitor-/181132488250?pt=Computer_Monitors&hash=item2a2c566e3aits an 8bit panel with FRC to 10bit? i dont fully understand it
anyway its got everything the u2412m has and its 2560x1440 with better colour reproduction, i moved from the u2412m to this. its incredible
so IMO either go for a 1440p monitor used
or
a dell u2412m new/used AND a second monitor in portrait next to it (make sure its IPS) tn monitors dont look good in portrait, a 1080p/1200p dell would be best
or you can actually afford 2x u2412m refurbished on here
http://www.amazon.com/gp/offer-listing/B005JN9310/ref=dp_olp_refurbished?ie=UTF8&condition=refurbished&qid=1367501322&sr=8-1for 200 dollars EACH
oh and perhaps have a look up on the yamasaki catleap 2b : 120hz.net
IPS, 1440p and 120hz via overclocking...have a read up on it and other korean monitors
Multimonitor and high resolution is a must for me
once you go 1440+ or multimonitor you never go back. seriously DO IT