[Val]

My favorite Chilean budget wine ever was Casa Lapostolle Rapel Valley 2003, about $12 at the time. The following years haven't been as good as that spectacular vintage. The bottle now has a new label, "Casa". They also make Cuv?e Alexandre, a better and more expensive wine that is as good as any in Chile.

Another great inexpensive Chilean Cab is Root 1.

[PhilNYC]

I would stand by the Santa Rita (Maipo Valley) recommendation I made above.  I consider this class of Chilean wine ($15 to $20 with ratings of low 90's by all the usual reviewers like Parker, Spectator, Enthusiast, etc.) to be the Chilean bargain now since the super Chileans like Conch Y Toro Melchor are selling over $60.  The Montes Alpha mentioned by the OP is in this  "bargain" class.

I had a couple of bottles of Santa Rita Reserve 6-8 years ago that were pretty good at around $9-10.  However, when a top Chilean breaks $50, I just have to wonder if the best values aren't in some of the old standbys that are yesterdays new to Messrs. Parker and crew.  $30 buys you a very serious Ridge zinfandel, $45-55 buys a top Rioja grand reserve (Muga or Marques De Murrietta Castillo Ygay).  Are these Chilean wines on par with wines of this caliber?  Everywhere that Parker goes, inflated prices are sure to follow.

+1 on the Santa Rita Reserva from that timeframe.  Also like the Santa Rita Medalla Real cabs. 

Other affordable Chilean wins I've liked are Veramonte Primus (2005), Los Vascos cabs (2005) and Mont Gras Quattro (forgot the vintage).

[woodsyi]

This 2005 Chilean Cab is probably too flowery for my taste but it seems to be a good value at $8.  I built a case with 6 bottles of this $12 2007 Mendoza Malbec to qualify for free shipping.  $120 for a case of (hopefully enjoyable) wine shipped.