Replacing a DVD / DVR

A friend is replacing a LG DR787T DVR that is on the way out.

I have a Gateway PC, Avermedia TV tuner card, wireless keyboard/mouse that runs Windows Media Center that totaled about $370. It works fine for me.

She wants to record over the air TV shows like on her DVR that burns to DVDs but she doesn't necessarily need to record/play DVDs since she just bought a DVD player. She would like to spend less than $300.

I initially thought net top box since it is a smaller form factor and they are complete which means less work for me. Any that I find recommended have already been discontinued or are really expensive.

Does anyone have a recommendation for one of these already to go for under $300?
Can I buy a ready built PC like my Gateway and add a card and get it in her price range?
Do I build from scratch and use Ubuntu to get a lot more for her money and maybe more headaches for me?
Do I buy a DVR for her and can I get one like Tivo but without a monthly fee?

Thanks,
Greg