Are you a professional sewer? Are you good at sewing? If the answer to either of these is no, save your money as what you have saved in not purchasing the off-sale perfect curtains will be lost in trying to make ill-fitting curtains work.

These look like nice curtains and I think they are already properly lined for that length. There is quite a bit of work to do so that they hang correctly

Actually adding length to curtain bottoms is pretty easy and straight-forward (but I sew) and can be done with fusible web if you don't sew. Or, and what I would do if I didn't sew, is take them to a good dry cleaner that does tailoring and repairs. If you have quite a bit of hem and heading you would only need to increase the length of the lining.

I've added length to drapes, but i've done it before. If you haven't then I would save the money, time and energy, and maybe frustration by puchasing something that is read to hang. They should also be hung close to the ceiling.

Yes, I am all about hanging curtains close the ceiling. I do have experience in sewing. If I decide to add a color coordinated solid panel to the bottom will it look good with the pattern of the drapes? I may have to suck it up and spend the extra money on the longer length.

Here is my take on this. Your goal is to make this added contrast look like it was part of the design, not curtains that were too short that you wanted to be longer. I like to add a bias cut cord between the original panel and the contrast, for a bit of added interest. In this photo, my client took her custom curtains to her new house and we reworked them. This technique does take a little more effort, but really makes a BIG difference in the outcome. For reference, her finished panels are 101", and I believe we went with a 12 inch contrast. I also used this contrast on soft cornices in the same room to tie it all together.

Purchase the correct length drapes. I've seen people try to add contrasting bands to pre-made drapes and more times than not, it looks bad.

Presuming you have the sewing equipment, workspace and patience, it all depends on how much cheaper these drapes are than the correct sized ones and how much you value your time. The basic question is "what do you have more of...time or money?"

I wouldn't even hassle with trying to lengthen these drapes unless you're talking $100 or more difference in price as there's potentially lots of hours fussing around to get them to hang right after you have started working on them. That said, I have taken drapes I've bought for a couple of bucks and let down the hems, steamed out all the creases and the stitching marks (not always possible...) and faced them with fabric of a similar color, fiber and weave and then added length to the lining to hide the facing. But, if you have better ways to spend your time, buy the right length and be done with the issue

....a little late for you, but one could, if you dont need them to really keep light out, and just want them for the looks of 'dressing' the window: make them 'fake' drapes....say only about 1.5 feet wide at top, and the rest of the width, cut off and add to the bottom...matching the print.