Switching ISPs Need Modem Advice!

Hi all. 

My current ISP is AT$T (I put the money sign because thats all they care about) and we pay for 6Mbps down and 1 or 2Mbps up all over DSL. 

Recently I convinced my Grandfather to switch to our semi-local (I think?) ISP Brighthouse Networks (knowing my luck they're probably owned by comcast or some shit lol).

He finally decided we would switch when he got a pretty good price offering from them in the mail. We already have standard cable through Brighthouse but our home phone and internet come through AT$T. So we will be ordering at least 30Mbps down and probably half that up from Brighthouse soon.

That's where the question comes in: We only have a DSL modem, a super old SpeedStream issued to us by AT$T probably before I was born. Obviously, I need a cable modem since Brighthouses internet is cable-based. I'm fairly sure Brighthouse will offer us one for some arbitrarily high price, but I'm not sure we should take it or not?

I know that ISP issued routers are a no-go, and I'm definitely not letting him accept a router from them, but I'm not sure if modems are any different? Would I be okay to take Brighthouses modem? Will it be under-preforming and over-priced? Maybe even just over-priced? 

If I shouldn't take theirs, can you suggest one for me to look at that is under like $80 or at least point me in the right direction for finding one? 

Thanks in advance, ~Tas

you have the option to lease a cable modem from them, otherwise  find a arris cable modem for a decent price, i tend to see almost anyone who uses cable have them. doesn't matter the isp.

Okay I found this one, it seems like it would do the job. Is there anything else I should know?

http://www.amazon.com/ARRIS-Motorola-SB6121-SURFboard-DOCSIS/dp/B004XC6GJ0/ref=sr_1_2?ie=UTF8&qid=1413361294&sr=8-2&keywords=arris+cable+modem

nope, just need to have them do a rolling test start on the modem or have a techniction come out and do it for you. and also. look into a vpn to be safe.. you never know who will be watching...