Well, you know, of course I will get an accountant, so this headache won't be mine. As for taxes, name me another EU country with lower taxes except Ireland, Cyprus and Bulgaria? I don't think that taxes are big at all, look at Germany, Netherlands, Belgium, France.
You've got social taxes to think about - which are the killer here. A Sp. Z.o.o will have to pay 20% on top of the gross salary, plus the employee will have to pay 17% of their gross salary in them. Dividends are taxable at 19% - but if you intend to pay yourself a monthly salary, you'll soon find the ZUS (social tax) payments starting to really bite. You'll also lose 18% of the gross salary in income tax too - so some figures.
Sp. Z.o.o has to pay 3600zl.
Employee pays 35% of 3000zl - so around 1000zl tax.
Added together, the cost to you will be around 1600zl a month to pay yourself 2000zl a month. Poland really isn't a low tax country, contrary to popular belief. Of course, if you can afford to pay yourself dividends or ride the edges of legality with tax laws, you might be able to pay less - but for an ordinary person trading through a Sp. z.o.o - it really isn't too great a deal.
PS I'm not EU national, so I can't be a Sole Trader here.
What country are you from? There are agreements out there that might allow you to be a sole trader in Poland.