I just want it to work for a while until I can get another amp
Do it. If you can get a good price on an LCD-4 now, but can't afford a 'duck's nuts' amp at the same time, don't worry about it. According to the math, 200mw will drive the LCD4 to painful levels and if the Magni 2 uber will do 320mw into 300 ohms then you should be more than fine to use it for a temporary solution without running out of room on your volume knob. Is it the end game audiophile amp for these headphones? Probably not, but your question was will it work until you can save up some more cash? Absolutely. If the LCD-4 price is too good to refuse I would go for it. If it's not that great a price, then I suppose it doesn't matter if you want to hold off too.
As long as you are the one that wants to buy the things of course and you're not just getting pressured into it...
According to:
https://www.audeze.com/products/lcd-collection/lcd-4 (scroll down to "specifications")
Audeze recommends 1-4W into their 200
Ω cans.
Might be tight.
- Dave
Last time I checked Audeze's website it recommended 1-4w for all their LCD's - even the X which is made for portable use. I think this is a case of either laziness in website maintenance, or Audeze just want you to spend up on a big headphone amp to reduce the chances of a customer doing something silly like plugging an LCD3 into an ipod and giving the 3 a bad wrap for being not that great. Could be a number of reasons but I would take that spec with a grain of salt.
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Go to here:
http://www.digizoid.com/headphones-power.html
and type in 200 into impedance and 97 into sensitivity and you can see the figures yourself.
Of course audiophiles will argue for the best, you want X times the RMS power for proper handling of transient peaks etc etc but that's not really the question - the question is will it work for the meantime, and the answer is yeah. Only other factor to consider that I can think of, is if your dac outputs a very low level signal, you won't get that quoted power out of the Magni's volume knob, but I think it would have to be something unusually low for it to not be a 'listenable' setup for now.