Hmmm .... Chinese New Year (of the Rabbit) for 2011 is on Thurs. Feb. 3, 2011 and your travel dates are getting very close to it - as local businesses begin to wind down for the holiday with many closing for 2 to 3 days or more to celebrate the transition from the old to the new. Oversea folks/expats return/fly home for the family reunion & some will be jockeying for flights & for the comfort of hotels in town - lodging prices tend to be adjusted (up) in response to market demands, limiting your value choices at popular in-town locations like TST & along the Nathan Road corridor, or across the harbour on HK Island side.

I would work those discounted sites & their search engines to pin down one and book it soon, and look at reviews posted at places like tripadvisors . com as reference.

If you are a solo traveler with light luggage, some of the newer boutique hotels in town rated at 3 stars might be good - standard category of rooms are small but full equipped, some with free internet included at no extra charge, and should be close to your price range (if not already sold out)

The Kowloon Hotel on Nathan Road in TST right above the MTR Station is rated at 4 stars but priced at $110 USD & with 10% surcharges like all others, rounding up to about $121 nightly on a quick booking check. Rooms are small but comfortable, tiny bath (like being in cabin of a cruise ship) - remodel recently but very convenient to shops, restaurants, waterfront & easy access to/from airport. Stayed there once and a visiting friend of mine was practically sitting outside the bathroom while talking to me with the "efficient" use of the angular layout of these rooms.

Several other popular tourist class hotels in the Mong Kok area rated at 2.5 stars or 3 stars are easily going over your $100 targets. The Metropark Hotel on Waterloo Street, rated at 4 stars is a bit farther away from the closest MTR but hotel has a free shuttle service and several of our local folks visiting gave it high marks, pricing might be higher than your budget for the given time frame (check it out - the related Metropark Mong Kok is 3 stars)