Kit aquariums are good when you are just starting out and have no earthly idea of what you are doing. I did that with my Fluval Accent 25 gallon kit. Fluval is a good company, but came at a premium for a "nice" tank. Now that I know what I am doing, any other tank I would get I would buy piece by piece. This past month I have been upgrading my Fluval accent. Everything inside of it has been upgraded, along with the filter, and lights while adding a CO2 system. To an untrained eye, it looks nothing like it has for the past 3 years. It is completely up to you.
My only advice is if you are not doing a kit, I would recommend (if you can afford it), buy the nicer equipment now so you only have to make a one-time purchase and piece of mind.