If you can afford it, I'd go with getting a TomTom.
The basic unit which is a TomTom Start you can get online for about £90.
They then can go up to stupid money depending on what features you want and what your budget is.
There's not point (IMO) in spending too much, some of the higher end features just aren't worth the money.
There are two reasons I say go for a TomTom.
Firstly I've found the interface to be logical and easy. This is very important when you think about it. The last thing you need when driving is to be faffing around trying to find the features you need or concentrating too much on what the map is saying.
Secondly, you can customise the TomTom with other voices easily. I think you can on some others but TomTom has the widest range. So you can have Darth Vader or Ozzy Osbourne directing you. A welcome change after a while from the stupid Jane voice.
A while back I bought a Garmin and took it back. It was nowhere near as easy to use as a TomTom.
You can get cheaper if your budget is limited. They'll all get you where you need to go.
Lastly unless you are likely to be driving abroad, give the Europe maps a miss. You are paying for a feature you won't use.