Mercury is setup. Now what?

After setting up mercury, importing my site (kinda), and switching Cache mode to External, I'm now getting some Varnish HITs...

Vanish History (varnishhist) shows low hit rate

I know I need to tweak Mercury to have Vanish cache more objects and return more hits, while also outputting an X-Varnish-Cache: MISS/HIT http header, but what else should I do with this Mercury setup?  What should I do about Memcache, Apache Solr? ...

Test it!

Going from a KnownHost VS3 768MB RAM server (shared between several sites) to a dedicated Linode 2048MB RAM server, I'm going to test the site before trying to mess with anything...

Siege test results on KnownHost - 768MB RAM, shared server:

        Date & Time,  Trans,  Elap Time,  Data Trans,  Resp Time,  Trans Rate,  Throughput,  Concurrent,    OKAY,   Failed
2011-04-29 13:22:34,    400,      22.48,          20,       1.08,       17.79,        0.89,       19.27,     400,       0 // homepage
2011-04-29 13:24:51,    400,      18.88,          11,       0.89,       21.19,        0.58,       18.77,     400,       0 // auto-deals
2011-04-29 13:26:06,    400,      11.68,           8,       0.57,       34.25,        0.68,       19.51,     400,       0 // dealer-price-quotes
2011-04-29 13:28:02,    400,      18.16,          13,       0.87,       22.03,        0.72,       19.18,     400,       0 // (Top 3 URLs, random)
2011-04-29 13:44:23,    400,      26.69,          21,       1.28,       14.99,        0.79,       19.21,     400,       0 // blog

        Date & Time,  Trans,  Elap Time,  Data Trans,  Resp Time,  Trans Rate,  Throughput,  Concurrent,    OKAY,   Failed
2011-04-29 13:31:25,    400,      24.41,          20,       1.18,       16.39,        0.82,       19.29,     400,       0 // homepage
2011-04-29 13:37:57,    400,      17.49,          11,       0.83,       22.87,        0.63,       18.91,     400,       0 // auto-deals
2011-04-29 13:39:19,    400,      13.44,           8,       0.63,       29.76,        0.60,       18.89,     400,       0 // dealer-price-quotes
2011-04-29 13:40:00,    400,      15.77,          13,       0.77,       25.36,        0.82,       19.44,     400,       0 //  (Top 3 URLs, random)
2011-04-29 13:45:34,    400,      26.31,          21,       1.28,       15.20,        0.80,       19.50,     400,       0 // blog

        Date & Time,  Trans,  Elap Time,  Data Trans,  Resp Time,  Trans Rate,  Throughput,  Concurrent,    OKAY,   Failed
2011-05-02 11:21:29,    400,      22.90,          20,       1.12,       17.47,        0.87,       19.49,     400,       0 // homepage
2011-05-02 11:22:23,    400,      15.79,          11,       0.77,       25.33,        0.70,       19.46,     400,       0 // auto-deals
2011-05-02 11:23:06,    400,      11.35,           8,       0.55,       35.24,        0.70,       19.29,     400,       0 // dealer-price-quotes
2011-05-02 11:23:57,    400,      15.98,          13,       0.78,       25.03,        0.81,       19.50,     400,       0 //  (Top 3 URLs, random)
2011-05-02 11:25:01,    400,      24.80,          21,       1.20,       16.13,        0.85,       19.31,     400,       0 // blog

Siege test results - Linode 2048MB RAM Mercury server:

        Date & Time,  Trans,  Elap Time,  Data Trans,  Resp Time,  Trans Rate,  Throughput,  Concurrent,    OKAY,   Failed
2011-05-11 12:43:23,    400,       0.74,           3,       0.04,      540.54,        4.05,       19.19,     400,       0 // homepage
2011-05-11 13:17:00,    400,       0.65,           2,       0.03,      615.38,        3.08,       19.37,     400,       0 // auto-deals
2011-05-11 13:17:39,    400,       0.67,           2,       0.03,      597.01,        2.99,       19.73,     400,       0 // dealer-price-quotes
2011-05-11 13:19:41,    400,       0.66,           2,       0.03,      606.06,        3.03,       19.79,     400,       0 // (Top 3 urls, random)
2011-05-11 13:20:08,    400,       0.86,           4,       0.04,      465.12,        4.65,       19.36,     400,       0 // blog

Vanish History (varnishhist) shows high hit rate