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IT pro here, just moved back to LV and not quite happy. Went with the ultimate package, consistent 100/10 vice the advertised 300/30. Netgear CM500, NIghthawk dual-core router, hard-lined. What up with that? In Tucson, had Comcast, 300+ all day....????
Sounds like your possibly bottle-necked by 10/100 link speed. Have you tried with CAT5e or above direct to the Netgear CM500 modem?
Also, where are you doing your speed test? Does the Cox one or DSLReports one report any difference?