Now that you have new gutters installed, when you get your next rain, put on your golashes (sp) and grab an umbrella and walk around the perimeter of the house to inspect the gutters. This would BEST be done in a heavy rain. (A light rain may NOT show you that the gutters do over-flow.) BUT, in any type of rain, you should also inspect the 'flow' of the water coming out of the downspouts. If you notice it pooling near the downspout or running BACK towards the house, well, you have your answer. The water needs to be channeled AWAY from the house. My rule of thumb: At LEAST 3' of downspout away from the foundation. You need to eliminate the negative slope towards the house (if any). If you notice that the volume of water coming out the downspout is not proportionate to the water going into the gutters, then either the downspout is clogged (and your gutters will runneth over eventually) or, if you have any part of your downspout 'system' underground, you have a leak.
I'm confused ... You're saying that you know the original drain field is working because water is being pumped out the sump pump. Yet, you say the contractor says that it was probably 'plugged up'. (Do clarify.) Now, let's assume that the slope ALL the way around the house is a positive slope. And that your gutters aren't over-flowing in a heavy rain, and that you've extended your downspouts 3' or more from the house, and there are no leaks. Then, you ask, where's the water coming from??? It would be tough to answer w/o being at the house. I do have one suggestion: Look in the Yellow Pages for Home Inspectors. Call one thats' ASHI-approved and have them do an exterior inspection. It may cost you a few dollars but negotiate it by describing your problem and seeing if they'll come out for $50 to $100. (Tell them you don't need a WHOLE-house inspection; just one to inspect why water might be coming into the basement.) It will be money well-spent considering that you may save yourself $$$thousands$$$ of $$$ from Contractor #1! The inspector can tell you what would need to be done in order to fix your problem. He should be able to give you a quote too. (If he offers to do the work, report him to ASHI; it's a conflict of interest.) Call around now and get a price BUT tell them you'll have them come out after you do an exterior inspection (as I described above) after the next heavy rain. This way, you'll have some answers for him. In the meantime, there's nothing to prevent you from extending your downspouts. Don't do any fixes to the grading yet until you talk to the inspector. Have him tell you the 'proper' grade and height to go with. Any of the Home Centers have 'attachments' and piping to extend the downspouts. Add up the total footage of piping you'll need and go to it! Forget about the 'looks' for right now. Your first priority is to prevent the water from getting into the basement.
If you need more help, post up. My best to ya and hope this helps.