First off design is a very subjective thing,it seems everyone has there own idea on what makes a good site, and what features it should have. I have seen sites, mine included that have received rave reviews, and then someone comes allong and say's i think the design is lacking and needs work?
So you need to do your homework, look at as many sites as you can, buy a few design, fashon magazines to get inspiration there are ton's of web sites devoted to design, one of my favorites is mocoloco.com That being said the first step is getting a designer, when you are first starting out and your site is small, you will only need a basic site, so amature or home made design, may be all you need, i would suggest go with a clean, minimal design, the site basschick points out is good, it is very similar to one of my blog sites www.jockblog.com i did the design of this site myself for nothing, as it is not a pay site, and i did not need anything too fancy. However once you start to build your sites content, you are going to need a more professional looking site, if you want to take your sales to the next level, it's just like CF said, eventually your customers will demand your site be up to par with your content. However here's where it get's tricky, over the past 10 years, i have worked with dozens of designers, who have built my sites, designed brochures, DVD box covers, print ad's etc I would say that 75% of the so-called designers out there, really are not that good, and lack the creativity you are going to want in a nice site, So you have to take your time and look around for the right designer, this can take some time, but it is important. I would first try nd get someone local, because the design process requires allot of fine tuning face to face with the designer. I should point out you can find the best designer in the world, who has done some amazing work, if you just drop off your content and a few ideas to him, and tell him to design your new site, it will more than likely look great from a visulal standpoint, but more than likely it will not convert very well with your surfers. This is why you will have to be in on the design process at every step. No one knows your content better than you, and what your customer/surfers want or are looking for. You will need the designer to take this into consideration when designing the tour pages, the photos, the navigation, everything. In otherwords you will have to know exactly how you want it to look, and then work face to face with the designer to create that look. Have a look at my 2 new sites www.jockbutt.com and www.markwolff.com hey if you don't think your own sites are fantastic then your in the wrong business, each of those sites took about 2 months back and forth with the designer until i got the home page and tour pages the way i wanted. Both those sites are 100% custom right down to the type fonts, the reason being my content is exclusive, i want my site design to create the same impression. These days 99% of the sites all look the same, if you are serious about building you web site and brand, you need to invest the time and money into a good custom site design. The bottom line with any site is how it converts, and that you see a increase in conversions from your last design, but you also want to create something that is different from every other cookie cutter design out there. So getting back to your question, i would use pro design however get the right designer, and one you can work face to face with. I should point out other than for banners i have never used a designer that works in adult, i have used allot of designers, that work mostly in the fashon and music business, i feel they have fresher ideas, but you need to know exactly what you want, and the look you you are going for, no designer can read minds or know how to convert traffic better than you. Hope this helps