Even the cheapest DSL modems can handle speeds much higher than you're being sold - so I doubt a better modem would give you better speeds.
Try running a benchmark speed test
http://www.dslreports.com/stest
Your ISP caps your speed - but you should be close to what they are selling you (Verizon has different speed packages so I won't speculate)
Good luck. You can always try searching "Verizon DSL tweak" or something in google as well and you'll be given a lot of good tips on how to get the best speed posssible.