We will be in Venice at the end of May...
Need a suggestion on Hotels...priced between
$300 and $425 per nite.

We just returned and stayed at Foscari Palace. Absolutely charming hotel. We loved everything about it. Recently remodeled with modern comforts, but still with all the lovely details of an old palazzo. The breakfast was outstanding, even included bacon and eggs. There was also a coffee maker in our room.
http://foscari.hotelinvenice.com/

We had a superior double (room 304). It was very spacious. The bath was fabulous: all marble, elegant fixtures, jacuzzi tub and multiple-head shower. Fluffy robes completed the sense of luxury. There was a nice private terrace (5' x 12') with patio furniture and a view of the Grand Canal.

The roof terrace was closed when we were there. I wish I'd gone up to see it, but it's said to be very nice in summer. The hotel has a bar. They also have a "soiree" every few nights: chamber music group in Renaissance costume, canapes and free champagne! Very elegant and relaxing. (Unlike many Euro hotels, this one has a real "lobby".)

It's only steps away from the Ca D'Oro vaporetto stop. Lots of shopping and restaurants right around the corner and it's only a 10 minute walk to San Marco.

topping this post for Bob. I'd help but my Venice hotels are much lower price range (Pensione La Calcina).

My wife and I stayed at Locanda Orseolo in a canal view room. This place is much less a hotel than it is a B&B. I mention this place because our canal view room was approximately 250Euro (~$300) which is the low end of your range. They are most notable for their customer service (super friendly, super helpful, they treat you like family). Our canal room was also quite spacious for Venetian standards but each room varies in size. They might be booked solid already though as they are quite popular.

Another place that I had my eye on, but did not stay is Charming House DD724 which has standard rooms beginning at 255Euro and a Suite can be had for 350 Euro (~$430) which is in your price range. Here is a review: http://www.mrandmrssmith.com/boutiqu.../venice/dd724/

Locanda Orseolo:
http://www.locandaorseolo.com/en/

DD724:
http://www.dd724.it/en_html/home.htm

I also recommend the Foscari Palace. I had a lovely 6 nights in November and will be returning for 7 nights this coming November. The raves on tripdvisor are true. It's a wonderful hotel!

We loved our stay at the Palazzo Sant'Angelo. Small, luxury hotel on grand canal, you can even get rooms with a balcony on the Grand Canal. You should be able to get a room in that price range. Web site is palazzosantangelo.com.